- Electrical Safety Authority
Guidelines for the Design, Installation, Operation &
Maintenance of Street Lighting Assets
Version 2
©Electrical Safety Authority
May 2015
Foreword
The Guidelines for the Electrical Design, Installation, Operation, and Maintenance of Street Lighting
Assets were created in response to electrical contact incidents experienced throughout Ontario. The ESA
invited stakeholders to participate in writing street light asset guidelines. The stakeholders represent
street light asset owners, contractors and consultants. The primary purpose of the guideline is to
document best practice information from professional practitioners for the safe electrical design,
installation, operation and maintenance of roadway lighting systems in Ontario to mitigate electrical
hazards to the public and comply within the requirements of the Ontario Electrical Safety Code (OESC).
Additions to this guideline shown in red and in italic include legacy installations not bonded to ground and
service entrance enclosures.
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Contents:
1.0 General
1.1 Scope
1.1.1 Responsibility
1.2 Summary of Incidents
1.2.1 Background
1.2.2 Sources of Contact Voltage
2.0 Design and Installation:
2.1 Components
2.1.1 Conductor / Cable
2.1.2 Connectors
2.1.3 Poles
2.1.4 Brackets
2.1.5 Luminaires
2.1.6 Receptacles – For Seasonal Lighting
2.1.7 Protection and Control
2.1.7.1 Control
2.1.7.2 Protection
2.1.7.3 Legacy Installations that are not bonded to Ground
2.1.8 Underground Ducting
2.1.9 Handwells
2.1.9.1 Best Practices
2.1.9.2 Recommendations
2.1.10 Service Entrance Enclosures
2.2 Seasonal Lighting
2.2.1 Background
2.3 Grounding and Bonding
2.3.1 Introduction
2.3.2 Definitions
2.3.3 The general Function of Grounding and Bonding in Power Distribution
2.3.4 The Role of Grounding and Bonding in Street Lighting
2.3.5 How to Achieve Effective Grounding and Bonding for Municipal Street Lighting
2.3.5.1 Which components require Grounding and Bonding?
2.3.5.2 Which Grounding and Bonding materials should be used?
2.3.5.3 Which methods of Grounding are acceptable?
2.3.5.4 What (if any) resistance standard should be determined for grounding?
2.3.5.5 What, how & when do we test the system?
2.3.5.6 How can a ground Systems’ resistance be lowered if targets are not
obtained?
2.3.5.7 How shall Street Lighting equipment be bonded?
2.3.6 The Impact of Grounding practices on equipment Function
2.3.7 Summary of Essential Minimum Requirements
2.4 Voltage Drop
2.5 Demarcation Points and Service Entrances
2.6 Inspection and Verification
2.7 Third Party Attachments and Regulation 22/04
2.7.1 Design
2.7.2 Construction
2.7.3 Third Party Attachments to Street Lighting Plant
3.0 Operation and Maintenance:
3.1 Minimum Maintenance Guidelines
3.1.1 General
3.1.2 The Ontario Electrical Safety Code (OESC)
3.1.3 Canadian Standards Association (CSA)
3.1.4 Non-Routine Maintenance
3.1.5 Routine Maintenance
3.1.6 Electrical Power Supply for other Facilities
3.1.7 Routine Maintenance and Inspection Reports
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3.1.8 Non-Routine Maintenance and Inspection Reports
3.1.9 Emergency Locates
3.1.10 Outcome Targets
3.2 Typical Lights-out Procedures - Troubleshooting
3.3 Detection and Testing Contact Voltage
3.3.1 Detection of Contact Voltage on Street Lighting Infrastructure
3.3.2 Detection Equipment
3.3.3 Verification and Measurement
3.3.3.1 Identify Suitable ground references
3.3.3.2 Eliminate capacitive coupling and obtain accurate, repeatable
measurement
3.3.4 Characterize Contact Voltage Source
3.3.5 Mitigation Steps
3.4 Safe Limits of Approach
3.5 Developing a Contact Voltage Detection Program
3.5.1 Should we develop a contact voltage detection (CVD) program?
3.5.2 What is the most effective way to combat contact voltage Hazards?
3.5.3 How often and extensively should we conduct CVD?
3.5.4 What elements should be developed in a CVD program?
3.5.5 Who will develop and manage the program?
3.5.6 Who should perform contact voltage testing?
3.5.7 What happens when we discover contact voltage?
3.5.8 Summary of Contact Voltage Mitigation Strategies
3.5.9 Conclusion
4.0 Management:
4.1 Pole Testing and Replacement
4.2 Condition Surveys
4.3 Expected Service Life of Roadway Lighting Assets
5.0 Appendices
5.1 Definitions
5.2 References
5.3 Other Documents for Information Purposes
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1.0
1.1
GENERAL
SCOPE
The scope of the guideline is inclusive of all roadway illumination equipment on public Rights of Way,
including lighting on traffic signal poles. The equipment consists of poles, luminaires, brackets,
photocells, lamps, relays, conductors, ducts, handwells, vaults, and associated hardware.
Non roadway illumination on or off Public Rights of Way, and all other illumination equipment not on
Public Rights of Way, is not included in this guideline. To further clarify, traffic signals, flashing beacons,
lighted pedestrian crossovers, park walkway lighting, parking lot lighting, sports lighting, area lighting and
bus shelters are not included in the guideline. Note that the out of scope installations listed in this
paragraph may also have contact voltage issues.
1.1.1
Responsibility
Public safety of the streetlighting system is the full responsibility of the Street Light Asset Owner (SLAO).
ESA expects the SLAO to have a process in place that ensures their system is maintained and operating
safely to mitigate electrical shock hazards to the public or their pets.
The requirement for the street lighting system to meet the rules of the OESC came into effect on January
2, 2002. Some installations prior to the effective date (legacy installations) do not meet the requirements
of the OESC. The ESA recommends the non-code compliant legacy installations are brought up to the
current requirements of the OESC. When the SLAO chooses to make the legacy installation compliant
with the OESC, following the requirements of Section 2.3.7 of this document will apply. However, if the
SLAO chooses not to bring the legacy installations in compliance with the OESC, Section 2.1.7.3 may
assist in reducing electrical shock hazards for these assets.
1.2
SUMMARY OF INCIDENTS
1.2.1
B ACKGROUND
In recent years there has been an increased amount of attention paid to the condition of low
voltage electrical distribution systems, including those supplying street lights. This can be
attributed to a number of high-profile incidents where members of the public have reported
receiving an electric shock after coming in contact with publicly accessible infrastructure. The
consequences of these incidents range from pedestrians reporting a “tingling” sensation to cases
which have resulted in fatality. Animals are particularly susceptible to such occurrences and there
have been numerous cases where pet dogs have been injured or killed after contact with
inadvertently energized structures in the public right-of-way. These issues can occur at any time
of year, but appear to be more common in the winter months, which can likely be explained by
the presence of melting snow and road salt. The media has reported extensively on these
incidents resulting in increased awareness by the public, asset owners, utilities and regulators.
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1.2.2 SOURCES OF CONTACT VOLTAGE
Ostensibly, these incidents are caused by contact between a person or animal and an
inadvertently energized structure. Such electrical shock occurrences are the direct result of a
failure of an electrical insulation system. The root cause of this failure can be attributed to one or
more of a list of causes, including:
a) Aged infrastructure
As an installation ages, electrical insulation on cables and connectors tends to become brittle
and may begin to crack, exposing energized components. This effect is accelerated by the
presence of moisture and other contaminants (road salt, for example) and by exposure to
freeze/thaw cycles.
b) Inadequate design
Improperly sized cables, connectors or ducts, lack of circuit protection and inadequate or lack
of grounding and bonding could cause electrical failure or contact voltage. Components
installed in below grade enclosures that can fill with water or ice should be rated accordingly.
c) Improper installation
Poor workmanship can directly result in a hazard to the public. Specific examples of this
include sub-standard insulation taping and connectors or other components not being
installed in accordance with the manufacturer’s instructions. Such components are tested and
qualified based on the assumption that they are installed properly; meaning that if they are
not the product is not guaranteed to perform as designed.
d) Accidental damage
Third parties may dig-in to a cable without knowing it, or compromise the integrity of a
structure when working nearby (for example, a number of below grade handwells have been
found to be filled with concrete after adjacent sidewalk work has been completed).
e) Rodent Damage
Rodents such as squirrels, mice and raccoons have been known to chew through wire or
connector insulation.
f) Vandalism/ Theft or Power
Unauthorized connections to supply circuits may be made using unapproved components or
work practices. Vandals may remove ground conductors or damage access covers, resulting
in exposed wires.
g) Insulation Destruction Testing
To determine presence of voltage in an underground supply cable, crews have been
“stripping” the insulation off the cable exposing the bare conductor and re-taping. One
incident root cause was found to have the insulation stripped and left bare in the handwell.
Often times, the compromised integrity of the conductor insulation results in a high-impedance
fault which goes unnoticed by the party responsible for maintaining the asset until reported by a
member of the public or identified through a mobile or manual voltage scanning program.
Experience has shown that any conductive structure in the vicinity of a cable fault has the
potential to become energized and pose a hazard to the public.
Table 1 describes street light system components and possible failure modes which could result
in a contact voltage occurrence. It should be noted that in addition to those components listed in
Table 1, a failure in the street light electrical distribution system could result in the energizing of
other structures as well, such as bus shelters, signs, traffic poles and fences.
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Table 1
Potential Sources of Contact Voltage in Street Light Systems
Component
Pole
Possible Cause of Energization
Direct contact with a pinched wire or
degraded connector insulation between the
pole (if conductive) and/or any conductive
attachments (such as cable guards). Note
that some normally non-conductive materials
(such as concrete) will conduct electricity
when wet.
Installing a ground electrode at each pole
and bonding of the neutral to the metal or
concrete pole where legacy installations not
bonded to ground exist. A break or open
neutral could energize the pole and earth
around the base of the pole.
Pole foundation or sidewalk bay
Exposed conductors (due to insulation
degradation, inadvertent damage such as a
dig-in, etc.) will cause a potentially
dangerous voltage gradient when water and
salt are present.
Pull-box or handwell
Below grade conductors and splices are
exposed to harsh conditions which can result
in accelerated degradation. Also, stripping of
the insulation and not repairing the insulation
in an approved manner or not repairing at all
can contact the metal lid. If the pull-box is
conductive, contact voltage will result if there
is direct contact or if water and salt are
present.
Distribution Panels
Pinched or exposed wires can contact the
panel enclosure and cause it to become
energized.
Luminaires
Luminaires mounted above a certain height
are not required to be grounded, and as a
results may become energized.
Rodent Damage
If wires are accessible to wildlife, they may
damage the electrical insulation resulting in
an exposed conductor.
Vandalism/ Theft of Power
Unauthorized manipulation of supply circuits
and/or related infrastructure can lead to
substandard installations due to unapproved
materials and improper work practices.
Additionally, voltage detected on surfaces which are bonded to the system neutral may not be a
result of contact voltage but the return current and the impedance of the return path may be the
result of an elevated neutral voltage. If concerned, the asset owner should contact the local
electricity distribution utility to determine the exact cause and follow-up actions necessary to
resolve the issue. In the meantime, the circuit should be made safe until the root cause is
determined.
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2.0
2.1
DESIGN AND INSTALLATION
COMPONENTS
2.1.1 CONDUCTOR / C ABLE
There are two categories of streetlight cable, one cable that runs between streetlight poles (bus)
and the other that supplies power to the luminaires (service drop). Cables shall be CSA certified,
meet the requirements of the OESC and shall have designation suitable for their applications.
Example, RWU90 can be used for direct buried installations while RW90 cannot be used for this
type of installation. In order to reduce mechanical damage to the cable insulation and reduce the
likelihood of contact voltage, an outer cable jacket should be used and/or higher cable insulation
value.
Types - The cable types that are typically used for streetlight installations are:
Streetlight bus – RW90, RWU90, TWN75/T90, USEI75, USEI90
Streetlight service – RW90, RWU90, NMWU90
The voltage rating for the streetlight cable shall be 300V, 600V or 1000V.
Conductor Material: The conductor material used for cable conductor is a matter of code
requirements and economics. However, the two most commonly used streetlight cable conductor
materials are copper and aluminum. A quick comparison of a copper and aluminum conductor
with equivalent size reveals the following: Copper has higher conductivity than aluminum
(aluminum has only about 60 percent of the conductivity of copper) and it is more ductile (i.e. can
be drawn out easier). Copper has relatively high tensile strength (the greatest stress a substance
can bear along its length without breaking apart). However, copper is more expensive and
heavier than aluminum conductor for the same conductivity. The lightness of aluminum conductor
makes it more favorable for overhead spans.
Size: Once the conductor material is selected, the size of the conductor is governed by the
required circuit ampacity and voltage drop. However, because streetlight circuits tend to be
relatively lightly loaded but long in length, voltage drop typically dictates the conductor size. The
conductor shall be sized according to the OESC and such that the voltage drop in the circuit from
the service entrance point to the last Street Light on the circuit will not exceed the accepted
voltage regulation of the ballast (for example, 10%-13% of nominal for constant wattage ballast).
See section 2.4 on Voltage Drop.
2.1.2 CONNECTORS
There are a number of different street lighting connectors currently available. The connector
should be designed for the environment in which it is to be installed and be compatible with the
conductors it is joining. When joining similar metals it is always desirable to use a connector
fabricated from the same material. When joining dissimilar metals (copper to aluminum), an
aluminum connector should be used. The connector insulation should be appropriate for the
environment, with below grade connectors designed and certified for submersibility. Other
considerations include the number of connectors to be joined, the size of those connectors, the
tools available to the installers and the amount of working space.
Some common connectors include:
• Block
• Split-bolt (not recommended)
• Wedge
• Wing nut
• Compression sleeve
Some common insulation types include:
• Tape (self-amalgamating, PVC)
• Heat shrink sleeve
• Cold shrink sleeve
• Pre-molded
• Gel-based cover
• EPDM Rubber cover
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*Note: Tape Insulation on split bolts is not recommended for phase connections as they have
been a root cause of contact voltage incidents.
2.1.3 POLES
General
There are generally four types of poles (based on material) used to support streetlight luminaires
and associated hardware, namely; wood, reinforced concrete, metal and fibre-reinforced polymer
(FRP). When selecting a pole for streetlight application, the pole must be able to withstand the
mechanical loading of the attached components (luminaire and bracket) and the weather loading
as specified by the applicable design code. CSA standard C22.3 No. 1 "Overhead Systems" can
be consulted for typical weather loading and overload factors that can be used in selecting the
appropriate pole. If flags, banners or any items that can add excessive wind or mechanical load
to the pole will be attached to the pole in the future, then the selected pole must have sufficient
strength to restrict the loading of these appurtenances.
1. Wood Poles
Wood poles shall be manufactured and tested in accordance with CSA standard O15.1 " Wood
Utility Poles and Reinforcing Stubs" . Wood poles can either be butt treated or full length treated
for protection against rot, fungi and insects in accordance with CSA standards O80 " Wood
preservation" . Full-length treated poles offer the advantage of allowing for future adjustment in
burial depth due to grade change without the need to worry about embedding untreated portions
of the pole in the ground. There are different species of wood poles which have different strength
characteristics, such as, western red cedar, Jack pine, Douglas fir, etc. However, CSA has
defined classes for wood poles to indicate the strength of the pole by specifying minimum tip and
butt dimensions and an ultimate load that the pole must be able to support when applied 0.6m
(2ft) from the tip. Pole class designation for wood poles are based on numbers with higher
numbers having lower strength (example a class 6 pole has breaking strength of 1500 lbs (6700
N) while a class 4 pole has breaking strength of 2400 lbs (10700 N).
The setting depth for wood poles depends on the pole length and soil condition; refer to CSA std.
O15 for nominal setting depths.
2. Reinforced Concrete Poles
Reinforced concrete poles shall be manufactured and tested in accordance with CSA standard
A14 "Concrete Poles". When used in corrosive environment, these poles can be treated with
special coating to inhibit corrosion. Re-enforced concrete poles can be manufactured in different
shapes and lengths and can be specified to include pre-drilled holes to ease installation.
The setting depth for concrete poles depends on the pole length and soil condition; refer to the
manufacturer for nominal setting depths.
3. Metal Poles
Metal poles are available in aluminum or steel either for anchor-base mounting or direct burial.
Special "breakaway" or "frangible" base poles are also available for certain road and traffic
conditions. The setting depth for direct buried metal poles depend on the pole length and soil
condition, refer to the manufacturer for nominal setting depths.
All metal poles must be bonded to the streetlight circuit bonding conductor. In addition, OESC
section 10 & 75 permits steel poles to be used as the grounding electrode for equipment mounted
on the pole and where the pole is directly embedded in soil and the portion of the pole in contact
with the soil is not coated with any non-metallic coating or covering. The use of the metal pole as
a grounding electrode must also be approved by the manufacturer of the steel pole.
Steel poles shall comply with all applicable requirements in the latest issues of the following
standards:
• CSA G40.20/ CSA G40.21 " General Requirements for Rolled or Welded Structural
Quality Steel/Structural Quality Steel"
• CSA G164 "Hot Dip Galvanizing of Irregularly Shaped Articles"
• CSA W59-03 "Welded Steel Construction (Metal Arc Welding)"
• OPSS 2423 “Material Specification for Steel Poles, Base Mounted”
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•
•
•
•
•
•
Aluminum poles shall comply with all applicable requirements in the latest issues of the
following standards:
ASTM B221 "Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars,
Rods, Wire, Profiles, and Tubes"
ASTM B26 "Standard Specification for Aluminum Alloy Sand Castings"
ASTM B108 "Standard Specification for Aluminum-Alloy Permanent Mold Castings
OPSS 2451 “Material Specification for Aluminum Poles, with cast aluminum Frangible
Couplings, Direct Burial”
OPSS 2452 “Material Specification for Aluminum Poles. Base Mounting”
4. Fiber-Reinforced Polymer (FRP) or Fiberglass Poles
There is currently no CSA design standard for FRP poles. However, ANSI C136.20 " American
National Standard for Roadway and Area Lighting Equipment - Fiber-Reinforced Composite
(FRC) Lighting Poles" and ASCE manual 104 " Recommended Practice for Fiber-Reinforced
Polymer Products for Overhead Utility Line Structures" can be used as the design guide for these
poles. FRP poles have been gaining more widespread acceptance as an alternative to wood,
concrete and metal poles due to their light-weight, high strength-weight ratio, high resistance to
corrosion and non-conductivity.
The setting depth for FRP poles depend on the pole length and soil condition, refer to the
manufacturer for nominal setting depths.
2.1.4 B RACKETS
There are many types of street lighting brackets available on the market today, and care should
be taken in selecting the right type for the right application. The bracket most commonly used in
streetlight applications with cobra head luminaries is a one-piece tapered elliptical aluminum
(TEA) bracket as shown Figure 1.
Some points to consider when selecting a bracket:
1. Pole location with respect to curb or roadway (length of bracket).
2. Bracket strength - the bracket must have sufficient strength to support the weight of
luminaire and wind loading on the luminaires effective projected area.
3. Type of pole - Wood or metal pole plate required.
4. Bracket rise – beware of maintaining proper clearances on distribution poles. See
section 3.4 for Safe Limits of Approach.
5. Bracket length – this impacts the reach required to position the luminaire.
Figure 1 Tapered Elliptical Bracket on Streetlight Pole
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2.1.5 LUMINAIRES
Luminaires for street lighting generally consist of one or more of the following components:
a) Light source and socket
b) Ballast assembly (including starting aid for H.P.S. lamps)
c) Reflecting elements or element
d) Refracting glassware or plastic enclosure
e) Housing or body complete with bird stop and optical filter where necessary.
For Street lighting luminaire classification refer to ANSI/IES RP-8.
Installation Standards and Specifications for Poles & Luminaires
The Ontario Provincial Standards (OPS) provide a comprehensive set of standard specifications
and
drawings in the administration of road building in Ontario. In general, OPS Section 6 is for
electrical
works. Specifically, OPSS 615 and 617 provide the specifications for the installation of
poles and
luminaires
OPSS 615 CONSTRUCTION SPECIFICATION FOR ERECTION OF POLES
OPSS 617 CONSTRUCTION SPECIFICATIONS FOR INSTALLATION OF ROADWAY
LUMINAIRES
BALLASTS
General
Most High Intensity Discharge (HID) lamps (such as HPS, MH, MV) require a ballast to start and
operate within the limits set out by the lamp manufacturer. These operating limits are developed
and published by lamp type and wattage by the American National Standards Institute (ANSI). To
operate a lamp properly, both ballast and lamp must be electrically compatible and must conform
to the same standard (e.g. "S50" for a 250W HPS lamp per ANSI). A typical ballast assembly
consists of a transformer (core and coil) - current limiting device, an optional capacitor for power
factor correction and an igniter (starter) for HPS and some low wattage MH lamps.
The function of a ballast is to provide sufficient voltage to start the lamp and/or to limit the current
to the operating value of the lamp. All ballasts have wattage losses which must be included in the
circuit load. Some ballast types have a high starting current which becomes an important factor
in sizing of the supply circuit components (fuses, breakers, relays and wires).
List of Available Ballast Designs
Low Power Factor Reactor Ballast (See Figure 2)
Used where line voltage exceeds lamp voltage, used only to limit the lamp current. Economical,
small, has a low p.f. about 50%. Not recommended where line fluctuations exceed ± 5%,
producing lamp wattage variations ± 10%. Starting current about 150% of operating current.
FIGURE 2 – LOW POWER FACTOR REACTOR BALLAST
High Power Factor Reactor Ballast (See Figure 3)
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The power factor (p.f.) is improved to nearly 90% through the addition of a capacitor across the
line. This reduces the total line current by approximately 50%, thus permitting doubling the
maximum number of lights that can be supplied from a given wire size.
FIGURE 3 – HIGH POWER FACTOR REACTOR BALLAST
Low Power Factor Autotransformer Ballast (See Figure 4)
In addition to the same characteristics and function of low power factor reactor ballast, this ballast
raises the line voltage to the value required to start the lamp.
FIGURE 4 – LOW POWER FACTOR AUTOTRANSFORMER BALLAST
High Power Factor Autotransformer Ballast (See Figure 5)
Same as low power factor autotransformer ballast above; however, through the addition of a
capacitor in the primary circuit the power factor is increased to approximately 90%, resulting in
the same advantages of high power factor reactor ballast above.
FIGURE 5 – HIGH POWER FACTOR AUTOTRANSFORMER BALLAST
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Constant Wattage (Regulator) Autotransformer Ballast (See Figure 6) – (CWA)
With the capacitor in series, the light output becomes more stable. With line voltage variations of
± 10% the lamp wattage varies only ± 5%. In addition to have a leading 90% p.f., this ballast
draws a line starting current that is lower than operating current.
FIGURE 6– CONSTANT WATTAGE AUTOTRANSFORMER BALLAST
Premium Constant Wattage Ballast (See Figure 7) – (CWI)
Same as constant wattage (regulator) autotransformer ballast above except the ballast has two
separate windings offering the advantages of an isolating transformer. A voltage variation of ±
13% causes the lamp wattage to vary by ± 25%.
FIGURE 7 – PREMIUM CONSTANT WATTAGE BALLAST
High Pressure Sodium Ballast Assemblies
High pressure sodium ballasts have a starting aid in the form of an electronic solid state circuit
which provides superimposed pulses of 2500 or 4000 V ± during starting (see Figure 8 ). This is
in addition to the normal magnetic circuit that controls the open circuit voltage and limits the lamp
current. A full range of lead or lag ballasts are available, giving a high power factor of 90% plus
or a low power factor of 50%. Because of the relatively high voltage starting characteristics of
these ballasts, the life span may be reduced when they are left connected to a defective or burnt
out lamp over an extended period of time. It is also extremely dangerous to attempt to change
lamps while the electrical circuit and ballast are alive. This results from the fact that a regular
starter will continually supply high voltage pulses to a burned out lamp, broken lamp, or an empty
socket. A “protected starter” can be used to eliminate voltage being supplied to a burned out
lamp, broken lamp, or an empty socket.
FIGURE 8 - CWI BALLAST WITH STARTER
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Low Pressure Sodium Ballast Assemblies
Low pressure sodium ballasts are the ‘Reactor Autotransformer’ type that show good stability
under varying input conditions. A 10% ± variation in the supply voltage will create less than a 4%
variation in lamp watts with a corresponding lamp lumen variation of less than 2%.
NOTE In both cases of sodium ballasts the supply voltage will affect the colour output of the
lamp if it is not held within the recommended tolerance, i.e. H.P.S. will appear rather pink and the
L.P.S. will appear too orange.
LED driver (current regulator) LED drivers effectively provide the same function as ballasts in
traditional lighting products. Drivers regulate power to the LED, thereby controlling the brightness
or intensity of the LED. The driver system converts the supply voltage to a DC voltage and
provides a DC output current to the LED. It holds the current at a constant level/output over
variable supply voltage ranges.
2.1.6 RECEPTACLES – FOR SEASONAL LIGHTING
Receptacles used on streetlight poles for seasonal lighting shall be of the ground fault circuit
interrupter (GFCI) type. These receptacles shall be provided with weatherproof covering as per
OESC for use in outdoor wet locations. However, experience has shown that while these
weatherproof covers work well when the receptacle is not in use, they do not provide sufficient
weatherproofing while in use and have resulted in numerous site visits to reset the GFCI. In order
to reduce the nuisance trips and the ingress of water/moisture into the receptacle, "while-in-use"
weather covers are recommended. These "in-use" weatherproof covers allow the receptacle to
be protected from weather elements even when a power cord is plugged in. See Figure 9
Figure 9 - In Use Weatherproof Receptacle Cover
The size of the receptacles used shall be 15 amps or as specified by OESC.
The "while-in-use" weatherproof covers should be constructed from high-impact, UV-resistant
Non-metallic material or sturdy, corrosion-resistant metallic material and shall be CSA certified.
2.1.7 CONTROL AND PROTECTION
2.1.7.1
CONTROL
The control of streetlight and/or streetlight circuits is typically accomplished with the use of
photo-electric controllers (photo-cell) arranged in one of the following manner:
• Individually-controlled streetlights
• Group-controlled streetlights
Individually-controlled streetlights (see Figure 10) consist of various secondary voltage
systems with each light directly connected to the secondary distribution bus at different
locations and individually controlled by a photo-cell mounted on top of the luminaire.
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May 2015
Transformer
Individually-controlled
streetlights with Photo-cells
Secondary Conductors
owned by LDC
Figure 10 - Individually-controlled Streetlight Circuit
Group-controlled streetlight circuits (see Figure 11) consist of an additional streetlight
conductor that supplies power to all the streetlights, which is owned by the streetlight
asset owner (Municipality). The additional streetlight conductor is connected to the
secondary distribution circuit via a service entrance switch and/or relay. The relay (or
contactor) is centrally controlled using either a photo-cell controller or a cascade. The
cascade is essentially a voltage signal from an existing streetlight circuit that is initially
controlled by a photo-controller. The cascade system consist of one group of streetlights
controlling the next group which can then control the next group and in theory can
continue indefinitely. See Figure 12 for streetlight schematic using cascade control.
Having too many groups of streetlight on a cascade system increases the risk of
complete “lights out” if the initial control fails. In each group of streetlights, there are
typically 10 to 14 streetlights served by one switch, one relay (or contactor) and one
photo-cell (or cascade) depending on circuit loading and voltage drop.
Relay (or contactor)
and/or Service
Entrance with Photocell
Streetlight Conductor
owned by Municipality
Group-controlled
streetlights
Transformer
Secondary Bus Conductors
owned by LDC
Figure 11 - Group-controlled Streetlight Circuit
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May 2015
L1
N L2
Photo-cell
controller
Secondary bus
L1
N
Cascade
wire
Relay
controlled by
Photo-cell
L
L
L
L2
L
L
L
L
L
Relay
controlled by
cascade
Secondary bus
controlled by
Figure 12 - Streetlight Circuits being initially controlled by Photo-cell and intermediate
cascade (not shown - service entrance switch and ground conductor)
Photo-Electric Controls
All photoelectric controls shall meet the design and testing requirements of the latest
applicable ANSI and UL standards:
• ANSI C136.10 " American National Standard for Roadway and Area Lighting
Equipment—Locking-Type Photocontrol Devices and Mating Receptacles—Physical
and Electrical Interchangeability and Testing"
• UL 773 " Plug-in Locking Type Photocontrols for Use with Area Lighting"
The photoelectric control shall provide reliable switching of high-pressure mercury vapour
and high- pressure sodium vapour lamps under the following environmental conditions:
0
0
• Ambient temperature range: -40 C to 65 C
0
• Moisture level: 96% relative humidity at 50 C
Photocontrols used in street lighting applications are generally the normally closed (NC) type
made to be "fail safe". That is, should there be a component failure other than in the
photocontrol relay itself, the relay closes, energizing the streetlight circuits.
2.1.7.2
PROTECTION
Streetlight Bus – protection for overload and line faults
Protection furnished for street lights shall be capable of handling the operating voltage of the
circuit involved and shall have the following characteristics:
• Service entrance disconnect switch (complete with fuse or circuit breaker) to be used
with dedicated streetlight circuits for protection. Service entrance shall be sized
according to the OESC. If luminaires are fed from a common secondary distribution
bus that supplies other load, the service entrance switch is not required but each
luminaire (or service wire to a group of luminaires) must be protected.
• Luminaire – fault protection for the luminaire and service wire is typically provided by
a inline, water-tight, electrical quick disconnect (load-breaking) fuse. This fuse
should be sized to prevent the service wire from being burnt down under fault
condition. Example: a #14 cu service wire will require a maximum fuse size of 15A.
When sizing the fuse for the luminaire(s), the lamp/ballast starting current and
momentary high inrush current should be taken into consideration to avoid nuisance
operation of the fuse.
• Human and Animals – in order to protect human and animals from electric shock in
case of a faulted circuit to conductive equipment, all non-current carrying conductive
components must be bonded together with a conductor of sufficient size. The
impedance of the complete ground-fault circuit (phase conductor and bonding
conductor) should be low enough to ensure sufficient flow of ground-fault current for
fast operation of the proper circuit protective devices, and to minimize the potential
for stray ground currents on solidly grounded systems - ref: IEEE std 141-1993.
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2.1.7.3
LEGACY INSTALLATIONS THAT ARE NOT BONDED TO GROUND
SLAO’s who are aware or discovered the legacy underground street lighting system did not
incorporate a bond wire or fuse links at each individual pole are trying to resolve the issue to
mitigate electrical shock hazards. The ideal and preferred solution is to rebuild the underground
street lighting system to meet the requirements of the OESC as outlined in section 2.3.7. If the
SLAO chooses not to install a new wiring system, the following may reduce the step and touch
potential hazards:
• Replacing the conductive pole with a non conductive pole;
• Adding ground fault protection* that will clear a ground fault at the source protecting the
underground circuit;
• Monitoring the streetlighting system for contact voltage with the use of detection
equipment as outlined in Section 3.3.
Note: * The OESC defines ground fault protection as a means of detecting and
interrupting a ground fault current at a level less than the current required to
operate the circuit overcurrent device.
2.1.8 UNDERGROUND DUCTING
In past and current practice of installing underground ducting for streetlighting, the ducts
terminate just short of the pole and the cables are then inserted through the pole’s wiring aperture
leaving bare cables (without duct) between the end of the duct and the pole.
Ducting should be a continuous system where the duct should end inside the poles below grade
aperture or pole footing and above the entrance point for direct buried poles. The current shape
and size of the pole’s wiring aperture may not allow for ducting to be terminated into the pole.
Pole manufacturers should be advised to change the shape and size of the wiring aperture to
accept 50mm PVC duct used for streetlighting. The ducting should then pass through this
aperture and continue up to the pole’s hand hole. This will eliminate dirt and debris collecting
inside the duct thus allowing for easier replacement of old or deteriorated cables.
Conduits
Conduits are typically used to provide mechanical protection for cables and ease of future
replacement. When conduits are used they shall conform to the following requirements:
Material – conduits should be constructed from non-metallic materials such as PVC, HDPE, etc.
The conduits and fittings shall be designed, manufactured and tested in accordance with the
applicable CSA or NEMA standards listed below.
The minimum installation depth of the conduit shall be in accordance with the OESC
Size - the conduit shall be sized in accordance with the OESC.
Standards - C22.2 No. 211.1, C22.2 No. 211.2, NEMA TC 7
2.1.9 H ANDWELLS
Handwells/junction boxes are a common component of streetlighting systems and are typically
used as follows:
• As a pull point where distances exceed the desired maximum for supply conductors,
• As an access point for changes in direction of underground ducts; this avoids pulling the
cables through a bend in the duct,
• As an access point where ducts are required to cross a roadway or enter a bridge
structure,
• As a branch location where multiple circuits in a single conduit continue in separate
directions
• Embedded in bridge structures, i.e barrier walls, sidewalks, abutments, etc., for
connection to bridge mounted lighting poles or underpass lighting.
Handwells are available in several material types and a variety of sizes. They are typically round
or square/rectangular in shape with either an open or closed bottom. The more common material
types include precast concrete (with cast metal frames and covers), polymer-concrete,
polyethylene, and PVC.
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2.1.9.1 BEST PRACTICES
Handwell Problems
In order to address best practices, it is first necessary to identify some of the shortcomings or
problems associated with the use of handwells.
The metal components require bonding to ground. These connections are typically a weak
link.
Most handwells are not suitable for deliberate vehicular traffic and are subject to collapse of
the cover and/or walls when travelled over.
The limited wall space makes it difficult to have more than one or two ducts enter the same
wall and any attempts to do so can result in affecting the integrity of the wall. This is more of
an issue with round concrete handwells.
There is little room for coiling of cables and therefore a good possibility exists for cables to
come in contact with the frame and cover.
Handwells are not water tight and can fill with water leading to deterioration of cable
insulation as previously noted.
2.1.9.2 RECOMMENDATIONS
To reduce the possibility of contact voltage it is recommended to use non-metallic handwells.
Where metallic handwells are used, all metal components must be bonded to the system
ground.
The location of handwells is important; most are capable of supporting an occasional nondeliberate vehicle load. If however, they will be subject to regular vehicular loading, a
handwell rated for such loads must be used. ANSI/SCTE 77 “Specification for Underground
Enclosure Integrity” provides guidance for selecting the right enclosure based on the site
conditions. In addition to the loading factor, handwells located in areas that may be subject
to “scraping” by a snow plough blade should be slightly recessed to prevent being “clipped’
by the blade.
Where multiple ducts are required to enter a handwell, careful design practice should be
followed to ensure that orientation of the ducts does not affect the integrity of the handwell.
Open bottom handwells can help resolve such conflicts by having some ducts enter through
the bottom and others through the side. Refer to the OESC for maximum number of
conductors in a box.
If the decision is made to make use of a larger chamber such as a maintenance hole, it
should be noted that the larger chambers are subject to confined space requirements of the
Occupational Health and Safety Act; this will impact maintenance procedures.
It is an OESC requirement that all non current carrying metal parts be bonded to the system
ground. Provision should be available to facilitate this requirement.
In order to mitigate the collection of water within the handwells, crushed stone is
recommended as a drainage pocket below each installation. In clay soils, it may be
necessary to provide a more effective drain for larger chambers, such as, a connection to a
drainage ditch or storm sewer.
2.1.10 SERVICE ENTRANCE ENCLOSURES
Service entrance enclosures provide shelter of the service equipment from the environment and
restrict access to members of the public. Common materials such as fiberglass, plastic or metal
are available and are either non-vented or vented. Existing locations have been found to show
evidence of condensation and corrosion of the service entrance equipment.
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The interior of a non-vented enclosure with an open bottom in direct contact with the earth or on
grade concrete slab, is classified as a Category 1* location. To help control the build-up of
condensation in the enclosure and the service entrance panel, the enclosure shall be ventilated.
*The OESC defines Category 1- the location is one in which moisture in the form of
vapour or liquid is present in quantities that are liable to interfere with the normal operation of
electrical equipment, whether the moisture is caused by condensation, the dripping or splashing
of liquid, or otherwise.
2.2 SEASONAL LIGHTING CONNECTED TO STREET LIGHT CIRCUITS
2.2.1 B ACKGROUND
Unlike electrical equipment that is required to operate 365 days per year, Seasonal Lighting
presents a unique challenge and risk. Typically, seasonal lighting operates for a limited period
during the Christmas season. Outside of this time period, electrical supply equipment may lie
dormant and unused for up to 10 months per year. Mechanical and weather related forces
continue to act on this equipment year round, however damage may not be identified for
extended periods. In many cases, seasonal outlets continue to be energized and as such,
continue to pose the same risk of electrical shock as during times of use.
To ensure this equipment continues to perform in an electrically safe manner, the following points
should be observed:
• An annual equipment inspection routine and record should be maintained by the
owner of the asset. This should include periodic inspection of all seasonal
equipment that is live throughout the year.
• Seasonally energized equipment should be inspected prior to energizing and use.
• When attached to LDC assets, equipment should meet local supply authority connection
requirements as determined by OESC rules and ESA Regulation 22-04.
All equipment and devices should meet CSA approval and be designed for the application. As an
example, weatherproof covers should protect the outlet at all times and be designed to allow for
protection of the male plug adapter. It is recommended to use “Weatherproof when in Use”
receptacle cover (See Figure 9). It is also recommended that the receptacle and loads be
attached to the plant, a minimum 3m above grade to discourage unauthorized connections.
Street Light Asset Owners (SLAO’s) must ensure that third parties receive authorization from the
Street Light Asset Owner to use this receptacle and the SLAO must ensure that the devices being
plugged in are being used as intended.
Electrical installation should be completed by a Licensed Electrical Contractor under Ontario
Regulation 570/05 made under Part VIII of the Electricity Act, 1998
Asset owners should consider public safety awareness campaigns, directing the public and
Business Improvement groups to contact the electrical supply authority or ESA should they notice
damaged or questionable equipment.
2.3 GROUNDING AND BONDING FOR MUNICIPAL STREET LIGHTING
2.3.1
INTRODUCTION
A thorough consideration of grounding and bonding theory and practice is foundational to the
design of any electrical system. The grounding and bonding standards chosen by the designer
will affect system performance, equipment reliability and safety factors for both humans and
animals. Of central importance is the fact that grounding and bonding methods play a major role
in the mitigation of 'contact' voltage hazards. This section will summarize the basics of electrical
grounding and bonding and attempt to guide the reader through the major issues as they relate to
municipal street lighting design.
Before designing a system, designers are cautioned to establish a design philosophy. The
designer must decide whether to simply comply with minimum code requirements or perhaps to
''raise the bar' where it is warranted. The OESC serves its function properly by establishing a
minimum across-the-board safety standard. It then becomes an engineering responsibility to
define design objectives which address functionality, reliability and risk analysis. Engineers and
designers must understand and address electrical safety issues and design safety into the
system proactively.
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The following recommendations attempt to incorporate information provided in the Ontario
Electrical Safety Code, IEEE standards 142 and 1100, MEA, MTO, and OPS publications and a
survey of articles from popular trade journals and engineering handbooks. Other recommended
references are BS 7671, IEC 60364, NFPA 70 and the NESC.
2.3.2 DEFINITIONS
The term 'grounding' refers to making an intentional, permanent, electrical connection between
an electrical system and the earth. The term 'bonding' refers to joining the non-current carrying
metallic components of an electrical system to each other to form a permanent, electrically
conductive path. Ultimately the bonding conductors connect to the grounding system at the
service entrance panel.
Bonding conductors are often loosely referred to as 'ground wires' even by electrical
professionals. A 'grounding' conductor actually connects the system to an earth electrode
whereas 'bonding conductors' interconnect equipment components. Grounding and bonding
conductors typically are either bare or are covered with green insulation.
Grounding and bonding conductors must have sufficient ampacity to carry any fault current that is
likely to be present and have sufficiently low impedance to operate protective devices and limit
voltage rise.
Impedance is the total opposition to current flow presented by a conductor. It is the sum of the
resistance, capacitive reactance and inductive reactance presented by the circuit element in
question. Its unit is the Ohm and its symbol is the omega. It is an important design factor since it
has an impact on breaker trip time, transient energy dissipation, lighting dissipation, arc flash and
other electrical characteristics of the system.
Ampacity is the current carrying capacity of a conductor expressed in amperes.
2.3.3 THE GENERAL FUNCTION OF GROUNDING AND BONDING IN POWER DISTRIBUTION
Grounding can serve many varied functions in electrical systems and it is of great importance that
the designer bear in mind 'why' grounding is done before jumping to the 'how' stage. To this end
it may be useful to briefly look at the general reasons for grounding electrical equipment before
delving into street lighting in specific.
To list some of its more common functions, grounding is specified where it is required to:
• establish a common voltage reference point
• control and stabilize system voltages
• promote effective RF transmission from antennae
• limit step and touch potentials
• provide cathodic protection
• provide a return path for clearing faults on high voltage power transmission and
distribution systems
• provide a sink for transient energy, electrical noise, electrostatic discharge and lightning.
As we shall see, only a few of these have any significance to street lighting system designers.
In contrast to grounding, bonding facilitates the operation of fuses, breakers and other protective
devices by providing a return path for fault current back to the source. An equally important role
for bonding is to reduce or eliminate any difference in potential energy (voltage) between metal
surfaces, structures or components. This is crucial because shock and arc hazards begin with a
difference in voltage between two points.
Finally, it should be noted that while grounding and bonding play a key role in electrical safety,
the designer must not ignore other effective means of protection such as isolation, clearance,
insulation, guarding, relaying, alarming and the use of warning labels; topics which are outside
the scope of this section.
2.3.4
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T HE ROLE OF GROUNDING & BONDING IN STREET LIGHTING
May 2015
Effective 'system grounding' at the power distribution panel is an absolute must for basic
compliance with the OESC, however for street lighting purposes there is really very little to be
gained by providing
'supplemental grounding' of equipment at the poles.
To provide poles with effective protection from lightning damage would require air terminals and
large ampacity 'down conductors' connected to the earth. To provide a substantial reduction of
step and touch potentials would require a significant investment in grounding by constructing a
ground mat around each and every pole which is not practical.
Finally, the earth cannot be relied upon as a return path for fault current or for the proper
operation of protective devices such as fuses and breakers because the impedance of the earth
is variable and is generally far too high to be effective on Low Voltage distribution systems such
as streetlighting.
In some cases, the inappropriate placement of ground rods has actually aggravated existing
problems, making matters worse by increasing the level of stray current or by creating ground
loops.
The key design consideration for protecting street lighting equipment from the hazards of contact
voltage is to provide for effective bonding and not to rely upon supplementary grounding. A
continuous, low impedance bonding system of sufficient ampacity can provide a fault current
return path that will operate breakers and fuses quickly and thereby remove contact voltage from
metal surfaces.
It is essential and worth emphasizing that bonding is more important than grounding in the role of
clearing faults and removing dangerous voltages at street lighting poles. Much literature has been
written on the subject.
2.3.5 HOW TO ACHIEVE EFFECTIVE GROUNDING AND BONDING FOR MUNICIPAL STREET
LIGHTING
2.3.5.1 W HICH COMPONENTS REQUIRE GROUNDING AND BONDING?
a) System Grounding and Bonding
The 'system' must be solidly grounded at the service entrance by connecting the neutral
terminal (aka the 'identified conductor') to the earth.
The term 'solidly grounded' refers to making a direct connection to earth, in contrast to
other methods of grounding where resistors, inductors and special transformers are used
to connect the electrical system to earth. Street lighting systems must be solidly
grounded and the grounding conductor must provide a continuous path to earth with no
intermediate devices.
Multiple bonding of ground and neutral at other points downstream from the service panel
contributes to the creation of 'objectionable currents' which can then create shock and
arcing hazards and as such represents a violation of the OESC. Be careful to bond
neutral and ground together, but only at the power distribution panel.
For system grounding purposes, the ESA will generally accept either two driven ground
rods or a grounding plate. Unfortunately the allowance of grounding plates by the code
has inadvertently promoted the seriously erroneous notion that one ground plate is as
effective as two rods. In fact quite the opposite is true. Plates were originally intended
only for situations where ground rods cannot be driven. The British code BS7430 makes
a point of clarifying the difference between rods and plates and the designer is cautioned
to research the subject further if this point is not well understood.
Street lighting power distribution systems should be solidly grounded. Depending upon
local soil conditions this will generally require two driven ground rods or multiple plates.
Additional electrodes may be necessary to satisfy this requirement. Performing an earth
resistivity study prior to specifying or installing equipment may be required.
b) Equipment Grounding and Bonding;
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All conductive surfaces in a street lighting system must be bonded to each other and to
the earth. Conductive surfaces and components include metal power distribution panels,
metal hand wells, hand well covers, metal and concrete poles, metal junction boxes,
junction box covers, relay and control panels, mast arms and luminaires.
This system of bonding conductors provides a continuous electrical path which permits
fault current to return from the equipment back to its source (the utility transformer).
Bonding conductors also provide an 'equipment ground', because they are connected to
the system earth electrode back at the service panel.
Providing additional supplementary ground electrodes at individual poles or at intervals
distributed between the poles would exceed OESC requirements. Traditionally each
municipality has developed their own standard practice in this regard. At this point the
designer is cautioned to ask why additional equipment grounding should be installed,
what purpose it really serves and should be able to justify the number of grounding
electrodes specified. Recommended guidelines are provided below.
2.3.5.2 W HICH GROUNDING AND BONDING MATERIALS SHOULD BE USED?
Grounding and bonding materials used for street lighting applications should all conform
to CSA C22.2 No. 41-07 “Grounding and Bonding Equipment” as a starting point. The
designer may also refer to OPS 609 and UL467 standards when specifying grounding
and bonding materials.
The following items should be specified in all municipal street lighting contracts:
a) Ground rods shall be 3.0 m x 19 mm (10 foot x 3/4 inch dia.) copper-clad steel
rods.
b) Ground plates shall be 254mm x 400mm x 6mm (10" x 16" x 1/4") galvanized
steel with a minimum surface area of 0.2 square meters.
c) Grounding Electrode Connectors shall be of the compression type and be rated
for direct burial. Exothermic welding is an acceptable alternative. Mechanical
connectors are unacceptable for direct burial applications unless specifically
approved for the application.
d) Bonding conductors will typically be a stranded copper wire. Refer to the OESC
for proper sizing. A #6 AWG wire is typical. Splicing is permitted where the
connections are accessible.
e) Ground electrode conductors will typically be a hard drawn stranded copper wire.
Refer to the OESC for sizing and installation instructions. Splicing is generally
forbidden unless an approved method is used. Soldering alone is not an
acceptable connection method.
f) Grounding grid conductors where used to interconnect grounding electrodes,
shall be large enough to ensure a degree of mechanical integrity. A #2 AWG
bare, solid copper wire is typical.
g) Ground enhancement compounds will reduce resistivity to earth and is readily
available from a number of suppliers.
h) Anti-corrosion compounds shall be applied to all mechanical lugs.
i) Hand wells where used should have sufficient strength for the application and
shall be fitted with a bolt-on, removable cover. Non-metallic types are preferred,
otherwise the cover and frame should be bonded to the system.
j) Street lighting equipment should provide 'ground' lugs' or 'pigtails' for bonding
purposes. This includes panels, poles, hand wells and luminaires. Equipment
which does not provide for electrical bonding should incorporate guarding or
insulation as an alternative means of protection from contact voltage.
Compliance with relevant CSA standards is a must. Mast arms may rely upon
clearances and insulation (rubber grommets) for protection from contact voltage
since most mast arm manufacturers do not provide a bonding lug.
k) Miscellaneous specifications may be required to cover utility locates, tamping,
surface restoration and site cleanup.
l) Clean surfaces; non-conductive protective coating such as paint or enamel are
used on the equipment, conduit, couplings or fittings. Such coating shall be
removed from threads and other contact surfaces in order to ensure a good
electrical connection.
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2.3.5.3 W HICH METHODS OF GROUNDING ARE ACCEPTABLE ?
This section discusses 'how' grounding should be accomplished and does not address
the issue of 'how much' grounding is required; 2.3.7 provides that information.
Municipal street lighting systems and equipment shall be solidly grounded using either
manufactured or “made” grounding electrodes as defined by the OESC. In-situ grounding
involves bonding to existing infrastructure such as building frames, rebar and water pipes
and is not recommended for street lighting applications.
“Made” electrodes consist of a bare copper conductor buried either directly in the earth or
in concrete and is a method accepted by the OESC. However, where the designer is
attempting to establish a solid earth connection for equipment grounding purposes, this
method should be augmented by incorporating additional electrodes of the manufactured
variety which are buried below the frost line in native soil. Street lighting system
designers may take advantage of this by using a bare bonding conductor buried directly
in the earth to provide supplemental equipment grounding.
Common manufactured electrodes include rods, plates and copper strips. Each has their
purpose and proper application, but where street lighting is concerned, designers should
be seriously looking at specifying a good quality ground rod. Of the three, a rod has far
superior “grounding characteristics”. Unlike a plate, it is able to distribute electrical
charges over a much larger volume of earth. Furthermore, when properly driven to its full
length it will penetrate into native soil and below the frost line whereas plates are
generally buried in much more shallow layers of earth where temperature, humidity and
resistivity are less stable and do not promote good conductivity.
Grounding specifications should require that rods be driven to their full length in a manner
which does not damage the rod. The OESC permits ground rods to be driven on an
angle if necessary.
Ground rods should be copper-clad for corrosion resistance and steel for strength.
Grounding electrodes must be properly spaced if they are to be effective. The optimum
spacing for a ground rod is twice its length which would typically be 6 meters and the
minimum spacing is the length itself which is typically 3 meters.
Spacing for ground plates is typically 2 meters and burial to a depth of 600 mm is
required.
A typical ground rod.
A typical ground plate.
2.3.5.4 W HAT (IF ANY) RESISTANCE STANDARD SHOULD BE DETERMINED FOR
GROUNDING ?
Establishing a maximum resistance standard for a grounding system is a valuable
method of ensuring that the intended electrical characteristics are being accomplished by
the design, that specifications are being followed by contractors when installing the
equipment and to facilitate the performance of annual maintenance checks.
Determining a specific resistance standard is however not a simple matter since it must
take into consideration system design objectives, economics, earth resistivity, existing
underground structures and other factors. Average earth resistivity may be 10,000 ohm-
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cm, low earth resistivity is defined as < 5,000 ohm-cm and > 20,000 ohm-cm is
considered high. High resistivity soils may necessitate the installation of additional
electrodes or the use of special methods to achieve your design objectives. Rock and
gravel are particularly problematic.
The NEC requires that a service be grounded with a maximum resistance of 25 ohms to
earth. This is approximately the value that one properly installed ground rod will yield in
soil of 'average' resistivity. The OESC does not specify a particular value, having
removed the old 10 ohm requirement back in the 1980's. Ten ohms is however, the
approximate value two properly installed ground rods will yield in soil of average
resistivity and ten ohms is a commonly specified value in many standards (see US Army
TM 5-690, MIL-STD-188-124A, FAA-STD-019d etc).
For this reason, street lighting designers should require that system grounding (at
the power distribution panel) yield a maximum value of 10 (ten) ohms to earth.
Supplementary grounding at street lighting poles however, is a separate issue.
Bonding is really the key to protecting human beings from contact voltage by means of
supporting effective fault clearance; we cannot rely upon the earth as a path for clearing
faults; we are not trying to construct a lightning protection system and placing a single
ground rod at each and every pole will not substantially lower step and touch potentials.
For this reason, street lighting designers should not rely upon or invest a significant effort
or expense in grounding poles. Where grounding at poles is deemed necessary, the
quality of the ground should however be verified. A ground rod placed at a pole should
not exceed 25 ohms of resistance to earth. This is a reasonable and attainable value that
will not generally require special materials or methods. Lower values are only justifiable
for generating stations, central offices, telecommunications towers etc.
The real issue then becomes one of, how many rods do we install at the poles? To
answer this question we must once again review our design objectives and ask ourselves
what it is exactly that we are trying to achieve. In consideration of both safety and
economy it would be best not to make an arbitrary decision. Unfortunately, no definitive
quantitative criteria exists upon which to set this value since no particular design
objective is served.
Old standards recommend grounding every fifth pole and the last pole in the system, but
since pole spacing standards vary greatly, this practice will yield varying results. As a
result the recommendation which follows is based on traditional power utility practice
instead.
In order to provide a nominal level of supplementary equipment grounding for step
and touch potentials, lightning, accidental contact with high voltage wires and a
measure of redundancy for the bonding conductor the street lighting design may
require the installation of one ground rod a maximum of every 300 meters.
It may be of interest to note that contact voltage and stray current hazards only exist in
the first place because we reference our electrical power transmission and distribution
systems to earth at the transformers. In most of North America we use a TN-C-S system.
This means that neutral and ground are combined up to the service and separate
afterwards. European designers may be familiar with a different system.
Furthermore, it is crucial that designers dismiss the erroneous notion that 'electricity
always exclusively follows the path of least resistance'. Nothing could be further from the
truth. In fact, electricity follows all available paths in inverse proportion to the relative
impedances of those paths, back to the source (the distribution transformer).
This is known as Kirchhoff's current law and it is because of this law that a faulted hot
conductor making contact with a pole will pass current through a human or animal body
to the earth and take this or any other path available back to its source. The problem is
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May 2015
that the low level of current (milliamps) that it takes to kill or seriously injure a human
being is far too small to operate a standard fuse or breaker.
Once again it is the bonding conductor that protects us. It provides a direct low
impedance path back to the source so that sufficient fault current will flow (as dictated by
Ohms law) which then operates the breaker or fuse and removes the source of power
until such time that trouble shooting and repairs can take place.
2.3.5.5 W HAT, HOW & WHEN DO WE TEST THE SYSTEM?
a) Earth resistivity studies shall be conducted using the standard 4 point, Wenner, fallof-potential method with a properly calibrated instrument prior to designing the
system.
b) Resistance to earth of a grounding system should be measured using a 3 point test
with a properly calibrated instrument. This test must be conducted prior to
connection and prior to energizing the system. Do not use a clamp-on instrument for
verifying the resistance of a newly constructed grounding system. Clamp-on
instruments can be useful for monitoring changes in existing systems once a base
line is established and can be used without disconnecting the ground electrode
conductor or de-energizing the system.
Resistance values obtained will vary with rainfall and temperature.
c) Many companies manufacture the required instrumentation.
Choose an instrument which filters out common circulating earth currents and
provides a low resistance range for testing bond resistances. Calibrate it on an
annual basis.
d) Leakage current to ground may be a useful measurement to make once the system
is commissioned.
2.3.5.6 HOW CAN A GROUND SYSTEMS' RESISTANCE BE LOWERED IF TARGETS ARE NOT
OBTAINED?
The resistance to earth of a grounding system can be lowered by the following methods:
a) increasing the number of grounding electrodes.
b) increasing the length (depth) and surface area of electrodes.
c) the use of horizontal grounding grid wires.
d) the use of ground enhancement materials such as conductive concrete.
e) the use of a more effective grid pattern (for example using a triad vs. linear row)
f) the use of exothermic welding or compression fittings rated for direct burial.
g) installing the rod in undisturbed soil away from the base is preferred
Ground electrode and bonding conductor impedances can be lowered by not coiling
excess wire in hand wells and by eliminating sharp right hand bends wherever possible.
Chemically enhanced ground rods are premium products available to install for street
lighting applications and may require special safety and environmental issues.
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2.3.5.7 HOW SHALL STREET LIGHTING EQUIPMENT BE BONDED?
Bonding shall be specified in such a manner to provide a continuous electrical path of
sufficient ampacity and low impedance to support the effective operation of protective
devices.
Bonding of neutral to ground in the service panel is usually achieved by a jumper or brass
screw located between the neutral bus bar and the equipment frame or equipment
grounding bus bar. Because this jumper is removable, it is important to verify the
presence and integrity of this main bonding connection at the time of installation.
Bonding to poles and luminaires is accomplished at designated 'ground' lugs or with
pigtail wires supplied by the equipment manufacturer. Concrete poles must provide for a
continuous bond between internal rebar (in the pole) and the ground lug provided.
Pole hand hole covers on non metallic poles should be of a non-metallic material. Where
a metal cover is used, consideration should be given to positively bonding the cover with
a bonding jumper rather than relying on the mounting screws for a solid bond. The
mounting screw shall be tamper proof.
Electrically bonding the poles to each other and to metal hand hole frames shall be
accomplished using stranded copper wire. This bonding conductor shall run continuously
from the equipment grounding bar in the service panel to the last pole in the system.
UTILITY
SERVICE
PANEL
LUMINAIRE
POLE
BREAKER
EQUIPMENT
NEUTRAL
FAULT CURRENT PATH
BONDING CONDUCTOR
GROUND
ELECTRODE
CONDUCTOR
HOT CONDUCTOR
NEUTRAL CONDUCTOR
GROUND
ELECTRODES
FUSE
SUPPLEMENTARY
Power Distribution Schematic Diagram
Page | 26
May 2015
2.3.6 T HE IMPACT OF GROUNDING PRACTICES ON EQUIPMENT FUNCTION
In addition to the previous recommendations, grounding and bonding specifications must take
into consideration equipment manufacturer's requirements. New technologies are emerging and
the street lighting designer must remain cognizant of new developments because they may have
implications for grounding and bonding.
Should the designer decide to specify Ground fault protection or detection equipment at the
power distribution panel, the requirements, limitations and characteristics of the grounding and
bonding system must be fully understood in order to achieve the design objectives Grounding
also has implications for harmonics and power quality issues that may require consideration.
Finally, and for future consideration, where electronic ballasts, LED's and adaptive lighting
methods are employed, it may be necessary to provide a superior standard of grounding to
support the function of Surge Protection Devices (TVSS), devices that are incorporated into many
modern electronic products.
Solar powered, LED Street light.
2.3.7
•
•
•
•
•
•
2.4
Electronic Ballast.
SUMMARY OF ESSENTIAL M INIMUM REQUIREMENTS
Follow the requirements of Section 2.1.7.2 Protection.
Bond all non-current carrying metallic components to the service ground bar.
Size all conductors, including the bonding conductor, to meet ampacity and impedance
requirements.
Connect the service panel neutral bar to earth using at least 2 ground rods.
perform inspection of the bonding system when installed
Meet or exceed all OESC and manufacturer requirements.
VOLTAGE DROP
All electrical equipment has a specified operating voltage range for normal operation. In order to meet
this voltage range, the voltage drop associated with the electrical circuit delivering power to the
equipment must be minimized. Streetlight luminaires are typically powered by ballast or a driver circuit (in
the case of LED luminaires) which has the capability of regulating the voltage output to the lamp.
The maximum permissible voltage drop from the point of power supply to the point of equipment
utilization shall not exceed the maximum percentage specified for each luminaire. Example, luminaires
supplied with CWI ballast can typically withstand a maximum voltage drop of 10% of the rated line
voltage. Therefore, for a 120V supply voltage these luminaries will operate effectively (minimal reduction
in light output) with a voltage drop of 12V. However, when streetlight circuits are to be installed on
sections of the distribution system where the primary voltage is lower than nominal, the voltage drop
allowable on the streetlight circuit should be adjusted to reflect the lower primary voltage. Also, in order
to allow for a margin of safety in the design, the manufacturer suggested maximum voltage drop should
be reduced. Hence, as a good design practice, the maximum voltage drop on circuits utilizing these
ballast (CWI) should be in the range of 9 – 10V. The maximum voltage drop may also be limited by the
fault current required to operate the protective device at the service entrance. That is, the circuit length
must be restricted to ensure that the impedance of the circuit is low enough to generate sufficient fault
current at the furthest luminaire to trip the upstream protective device in a timely manner.
In order to calculate the voltage drop along a streetlight circuit, the following information should be known;
• conductor type and size (determines the Impedance per unit length), Z
• segment length (length between each luminaire), L
• load drawn by each luminaire (i.e. lamp wattage plus ballast load), I
The conductors (wire) carrying current to the luminaires in the street lighting system have a small amount
of impedance (resistance and reactance). The impedance of the wire depends on the size of the wire,
Page | 27
May 2015
the material of the wire, the length of the wire and the temperature of the wire. When current flows
through the wires on its way to the luminaires, a voltage drop proportional to the impedance and the
current is developed along the length of the wire. This voltage subtracts from the voltage at the source of
power (voltage drop) and results in a lower voltage at the luminaires. If the impedance of the wire is too
high for the amount of current flowing through it, the voltage dropped along the wire will be too high to
allow sufficient voltage at the luminaires. High resistance can also result in conductor overheating. The
2
square of the current (I ) flowing through the wire multiplied by the resistance of the wire (R) yields the
2
power dissipated in the wire as heat (I R). Therefore, the higher the resistance of the wire, the higher the
voltage dropped along the wire, and the more power is used up by the wiring system. The OESC
suggests a value of 5% of the system voltage as the maximum allowable voltage drop in a lighting branch
circuit. However, for Roadway Lighting Systems (such as streetlight circuits), OESC 2009 Bulletin 75-6-*
permits the voltage drop to exceed 5%, provided that the voltage drop does not result in a voltage at the
luminaire that is outside the rated operating voltage limitations of the luminaire. This is applicable on
dedicated streetlight circuits only.
The voltage drop calculation determines the size (gauge) of wire of a specified material that is
necessary to carry the required current the required distance without creating too large of a loss
in the wire.
The voltage drop along each segment can be found by using the following approximation:
Vd=I* Rcos +IXs in
Where:
Vd
I
R
X

Cos
Sin
is the voltage drop along a segment of wire
is the current through the same length of wire
is the resistance for the segment of wire
is the reactance for the segment of wire
is the load angle
is the load power factor
is the load reactive factor
It should be noted that the above equation is an approximation but gives very accurate results for typical
streetlight circuits
The values for R and X can be obtained from manufacturer or via published data such as tables in IEEE
std 141 “IEEE Recommended Practice For Electric Power Distribution for Industrial Plants” and the NEC
(National Electric Code).
The current, I, for any segment of wire is calculated by adding the currents for each luminaire the
particular segment of wire feeds (i.e. all the luminaires downstream on that wire). The Resistance, R, and
Reactance, X, for a particular segment of wire is calculated by multiplying the length of the wire in that
segment by the impedance per unit length (e.g. ohms/km) of wire for that particular size and material of
wire. The total voltage drop to the farthest luminaire is calculated by adding the voltage drops for each
segment of wire from the service entrance (or supply point) to that luminaire.
When calculating the voltage drop for a circuit, the voltage drop must be calculated for the phase wire
(hot wire) and for the neutral wire. This is especially true for a two-wire circuit in which the current that
travels out in the phase wire must return in the neutral, and so the current in the neutral wire is the same
as the current in the phase wire. The total voltage drop in the two-wire circuit, then, can be calculated by
determining the voltage drop in just the phase wire and multiplying that number by 2 (assuming that both
wires are the same size and type). Alternatively, the impedance per unit length can be doubled
(multiplied by 2) and proceed with the normal voltage drop calculation.
On three-wire systems (two phase wires and one neutral), the neutral current represents the sum of the
two phase currents. However, the phase currents are opposite each other and if the phase currents are
equal, then the total neutral current will be zero. That is, the current returning in the neutral wire from one
of the phase wires will cancel out the current returning in the neutral wire from the other phase wire.
Therefore, if the loads on the two phase wires are balanced, there will be no current in the neutral wire,
hence, no voltage drop in the neutral wire. In this case, the total voltage drop to the farthest luminaire is
simply the total voltage drop in the phase wires, and the neutral wire can be disregarded.
Page | 28
May 2015
VOLTAGE DROP EXAMPLE
Supply voltage: 120V
Streetlight bus: 2-#4 Cu USEI75 Cable (characteristic phase impedance = 1.956 ohms/km)
Luminaires: 150W HPS (1.67A total lamp load) spaced at 30m apart
Service entrance/Source located 20m away from first luminaire.
Assume that maximum voltage drop will be at luminaire #10
1
2
3
4
5
6
7
8
9
10
11
12
Street Lighting Voltage Drop Calculation
November 23, 2010
Project: ESA Streetlight Working Group - Example
File:
Load Power Factor (cosφ)
Load angle, φ
0.9
0.451
rads
Span
Resistance
Reactance
Impedance
Load Current At Luminaire
To Next
To Next
To Next
To Next
From
From
From Last
Luminaire, L Luminaire, RL Luminaire, XL Luminaire, ZL Luminaire
Branches
Luminaire Total Load, I
Luminaire No. & Size
(m)
(ohms/km)
(ohms/km)
(ohms/km)
(A)
(A)
(A)
(A)
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Transformer
Relay
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
150W HPS
0
20
30
30
30
30
30
30
30
30
30
30
0
0
0
0
0
0
0
0
0
0
0
0
1.71
1.71
1.71
1.71
1.71
1.71
1.71
1.71
1.71
1.71
0
0
0
0
0
0
0
0
0
0
0
0
0.487
0.487
0.487
0.487
0.487
0.487
0.487
0.487
0.487
0.487
0
0
0
0
0
0
0
0
0
0
0
0
1.778
1.778
1.778
1.778
1.778
1.778
1.778
1.778
1.778
1.778
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0
0
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
1.08
0.00
0.00
0.00
5.0
23.37
23.37
22.29
21.21
20.13
19.05
17.97
11.88
10.80
9.72
8.64
7.56
6.48
5.40
4.32
3.24
2.16
1.08
0.00
0.00
0.00
0.00
23.37
23.37
23.37
22.29
21.21
20.13
19.05
17.97
11.88
10.80
9.72
8.64
7.56
6.48
5.40
4.32
3.24
2.16
1.08
0.00
0.00
0.00
Voltage Drop
Accurate
To Next
Total at
Luminaire Luminaire
(V)
(V)
0.000
0.000
1.228
1.171
1.114
1.058
1.001
0.944
0.624
0.567
0.511
0.454
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Max. volatge drop
Characteristic Impedances of Standard Street Lighting Conductors - KWHydro
(Phase + Neutral)
R
X
0
0
1.228
2.399
3.513
4.571
5.572
6.516
7.140
7.707
8.218
8.672
8.672
8.672
8.672
8.672
8.672
8.672
8.672
8.672
8.672
8.672
8.7
Typical Lamp Loads
Z
70W HPS
0.83 A
0
100W HPS
1.08 A
0
150W HPS
1.67 A
0
200W HPS
2.08 A
0
100W MH
1.13 A
0
175W MH
250W MH
1.75 A
2.33 A
1-4/0 Al & 1-2/0 ACSR overhead quadruplex
0.687
0.412
0.80
ohms/km @ 25 C
1-#2 Al & 1-2/0 ACSR overhead duplex
1.278
0.436
1.35
ohms/km @ 25 C
1-#4 Al & 1-4 ACSR overhead S/L cable
2.765
0.504
2.81
ohms/km @ 25 C
2-#4 Cu underground S/L cable
1.710
0.487
1.78
ohms/km @ 25 C
2-#1 Cu underground S/L cable
0.845
0.459
0.96
ohms/km @ 25 C
HPS - High Pressure Sodium
MH - Metal Halide
Terminology:
Source <---------------[]------------------------------[]-------------------------------[]-----------------------------[]
Next Luminaire
Luminaire
Last Luminaire
Calculated voltage drop = 8.7 V
% Voltage Drop = 8.7/120 = 7.25%
2.5
DEMARCATION POINTS AND SERVICE ENTRANCES
Page | 29
May 2015
Demarcation points play a role in determining which party owns existing electrical infrastructure in the
field. Demarcation points play a larger role at present than they did in the past.
For most Ontario municipalities, the implementation, growth, operation and maintenance of street lighting
systems were originally handled entirely by the LDC. By consequence the street lighting systems grew
up together with the hydro distribution systems with little difference made between the two (components &
wiring practice).
As of January 1, 2003, most Ontario municipalities have been assuming ownership of the street lighting
systems which exist within their region. They also have been assuming the management responsibilities
which the LDC previously undertook. This has resulted in the present day scenario in which
municipalities and their LDC must work to differentiate between the municipal street lighting system and
the hydro distribution system.
To complicate this matter further, there is no consistent standard across Ontario detailing which party
owns which electrical infrastructure in any given application; it differs from municipality to municipality.
In some instances this matter has proven to be highly contentious, as the demarcation points on existing
infrastructure may be undefined. This has resulted in, and may continue to result in:
1. Both the LDC and SLAO failing to locate a buried cable under the assumption that the cable belongs to
the other party,
2. Both the LDC and SLAO failing to maintain degrading electrical wiring under the assumption that the
wiring belongs to the other party. This may result in potential shock hazards.
As such, greater emphasis must be placed to establish a solid demarcation point on all existing
infrastructure. It is recommended that each SLAO and LDC define and document which assets each
party owns and is operationally responsible, especially as it pertains to electrical shock hazard mitigation
and keeping the general public safe. This is particularly important for underground cable locates.
The following illustrations are examples of the multiple demarcation point scenarios possible within
existing conditions and exemplify the need for clearly defined demarcation points such that both the Asset
owner and the LDC are aware of what infrastructure they own and maintain.
1st Scenario: LDC Secondary Feeding both SL and all other customers along bus
SLAO owned
Street Light Pole
LDC Customer
SLAO owned wiring
beyond fuse
Fuse acts as
demarcation point
LDC owned wiring prior
to fuse
LDC Secondary Feeding both street
lighting and other customers
Direct Connection
Illustration 1-1 (above) – LDC Bus feeding both Street Lights and customers. Street Light Poles
are SLAO owned with fusing located in the hand hole.
Page | 30
May 2015
SLAO owned
Street Light Pole
LDC Customer
SLAO owned wiring
beyond T tap
LDC Secondary Feeding both street
lighting and other customers
Direct Connection
Acts as demarcation point
Illustration 1-2 (above) – LDC Bus feeding both Street Light and customers. Street Light Poles are
SLAO owned and un-fused.
nd
2 Scenario: 3 Examples of how wiring ownership can be defined in a single scenario.
LDC feeding dedicated street lighting bus. Street light poles are SLAO owned with fusing located in the
handhold.
SLAO Street Light Poles
SLAO owns all
wiring
Dedicated Street Light Bus
Demarcation Point
Illustration 2 – 1 (above) - The SLAO owns all wiring infrastructure directly out of transformer
including the street light bus.
Page | 31
May 2015
SLAO Street Light Poles
Demarcation
Point
Hydro owned
wiring
SLAO owned
wiring
Dedicated Street Light Bus
Illustration 2-2 (above) - The SLAO owns all wiring after the fuse located in the first pole
SLAO owned Street Light Poles
SLAO owns all
wiring in poles
after fuse
Demarcation
Points
LDC owns all underground wiring
Illustration 2-3 (above) - The SLAO owns the wiring in the pole only, between the fuse and the
street light. In this case the LDC owns all underground wiring.
Page | 32
May 2015
In new street lighting installations, it is recommended that the point of demarcation be defined as the
service entrance for the street lighting systems or the street lighting pedestal. The street lighting pedestal
itself is generally owned by the SLAO (See Illustration 3 below).
SLAO Street Light Poles
SLAO owned SL
Pedestal is the
demarcation point
LDC owns
wiring
feeding SL
SLAO owns all
wiring beyond
SL pedestal
Illustration 3 (above) – Demarcation point practice for new street lighting installations.
It is suggested the street lighting pedestal be physically located in an area where accidents causing
physical damage to the pedestal are least likely to occur. An example of this is to place the pedestal
away from any intersections.
In new street lighting installations in which there is only one street light being added to the existing hydro
grid, then the in-line fuse will act as the demarcation point. Typical examples of this is when the SLAO
wishes to add a single street light to an existing hydro pole with existing hydro secondary already in
place.
For Overhead installations, refer to OESC Bulletin 75-6-*
2.6
INSPECTION AND VERIFICATION
The Ontario Electrical Safety Code requires a contractor to file with the inspection department of the
Electrical Safety Authority (ESA), a completed application for inspection of any work on an electrical
installation before, or within 48 hours after, commencement of the work.
Contact number for taking out an application for inspection is:
1 877 ESA SAFE (1 877 372 7233)
The site or location is required to be made accessible to the ESA inspector. Wiring shall not be concealed
until it has been inspected
Once ESA has determined the installation is in full compliance with the Ontario Electrical Safety Code, a
Connection Authorization will be issued to the LDC allowing the energization of the equipment. A
certificate of inspection will be issued to the contractor.
The asset owner may require an inspection of the installation prior to energization to ensure municipal
standards have been met, separate from the ESA inspection.
Page | 33
May 2015
2.7
THIRD PARTY ATTACHMENTS AND REGULATION 22/04
Licensed Distribution Companies (LDC’s) are required under Ontario Regulation 22/04 to design,
construct and maintain electrical distribution systems they own up to 50kV to the customer’s demarcation
point. The regulation is objective based and relies on Engineer approved standards meeting the minimum
requirements of CSA.
2.7.1 DESIGN
Third party attachments such as telecommunication equipment, street lighting, decorations, signs
etc. are not part of the distribution system. However, to the extent these attachments may affect
the safety of the distribution system, they may be indirectly subject to the Regulation. Hence,
prior to authorizing third party attachments, the distributor is to ensure that attachments to its
distribution systems meet the safety requirements of the Regulation.
Authorizing the third party attachments may be as simple as confirming that the
equipment installations that are being proposed by a third party are consistent with the
distributor’s Standard Designs. Alternately, the authorization may require detailed
evaluation, by the distributor or the third party, to determine whether the attachments
meet the safety requirements. In granting approval for attachments, the distributor is to
note limitations and requirements that are relevant to its applicable Standard Designs or to
the plan submitted.
2.7.2 CONSTRUCTION
For third party construction, the distributor should ensure that the construction is in compliance to
its Standard Designs or to an approved plan. The distributor could inspect the site using a
qualified person or require assurance of construction compliance to Standard Designs or to
approved plan from the third party. Any variation from Standard Designs or plan should be noted
for resolution by the owner in the record of inspection.
Once the inspection record has been prepared and all non-compliances have been rectified the
distributor can prepare and issue a Certificate (*). The purpose of the Certificate is to ensure that
there is no negative impact on the distribution system by the third party installation and does not
require the approval of the third party’s equipment by the distributor. In these installations, it is
likely that the construction will be placed into service by the third party prior to a Certificate being
issued.
When a distributor determines during the course of its operation that a third party attachment
does not comply to its Standard Designs or approved plan, the distributor should advise the third
party of the non-compliances and could pursue additional remedial solutions through its
attachment agreements. Where the third party does not rectify the non-compliance within a
reasonable time, the distributor may notify ESA, who in turn may carry out its own investigation.
(*) Note: The issuance of a Certificate by the distributor is subject to the cooperation afforded by
the third party.
2.7.3 T HIRD P ARTY ATTACHMENTS TO STREET LIGHTING PLANT
Street lighting asset owners will often find third party attachments on their plant without any prior
notification. Street lighting infrastructure is often used to support temporary communication
system repairs. The party attaching to street lighting assets is required to obtain permission from
asset owners prior to installing any plant. The street light asset owner must ensure that their
asset will support the proposed third party attachment. The installation of banners on street light
poles is especially critical to ensure that the forces created by wind loading are supported by the
street light pole. Asset owners are encouraged to investigate the use of third party attachment
agreements so that all parties understand the liabilities and responsibilities
Page | 34
May 2015
3.0
3.1
OPERATION AND M AINTENANCE
MINIMUM MAINTENANCE GUIDELINES
3.1.1 GENERAL
The Roadway Lighting System should be maintained according to this guideline. Defects in the
Roadway Lighting System should be identified, documented, and corrected by appropriate action,
whether by Routine Maintenance or Non-Routine Maintenance.
3.1.2 T HE ONTARIO ELECTRICAL S AFETY CODE (OESC)
The Ontario Electrical Safety Code identifies that work performed on Roadway Lighting Systems
must be inspected by the Electrical Safety Authority (ESA). Inspections and permits may be
requested individually, or an annual inspection agreement may be entered into with the ESA by
completing the “Contractor Application for the Inspection of Electrical Maintenance Work
Performed on Roadway Electrical Systems”. This application and additional information can be
found on the Electrical Safety Authority’s website at www.esasafe.com. Copies of all ESA
inspection reports should be kept on file.
3.1.3 C ANADIAN STANDARDS ASSOCIATION (CSA)
When required for the purposes of the electrical work, all electrical components shall be
according to CSA requirements. Provincial, Federal and local laws and by-laws pertaining to the
electrical work, as well as, by the latest issue of CSA Standards pertinent to the electrical work,
shall govern all electrical work. In the event of conflict of regulations, the strictest regulation shall
apply.
3.1.4 NON-ROUTINE M AINTENANCE
Non-Routine Maintenance is required whenever there is a Critical Failure of any system
component of the Roadway Lighting System or whenever vehicular accidents, weather or other
factors have caused damage to System Components. Critical Failures of the Roadway Lighting
System are identified in Table 2 below.
After detecting or being made aware of the Critical Failure, Non-Routine Maintenance should be
initiated in a timely manner.
Table 2
Critical Failures in the Roadway Lighting System
Critical Failure
Aerial Span Wire Down
Pole Knocked Down or Hit
Power Supply Knocked Down
Power Supply Failure
Ground Fault
Presence of Voltage on Non-Current Carrying System Components
Energization of Surfaces Accessible by the Public
Overhead equipment unfastened or hanging over roadway
Damage that exposes the public to energized electrical equipment
( e.g. vandalism )
Faulty Photo Control Circuits for Group Control of Lighting
Unbalanced, unlatched or partially unlatched high mast lighting ring
Failure of a Pole, Arm, or other Structural Element
3.1.5 ROUTINE M AINTENANCE
Routine Maintenance activities should be completed on all Roadway Lighting Systems and
should include:
• Inspecting, checking, elementary testing, cleaning, lubricating and performing minor
repairs on all Roadway Lighting System Components including luminaires, lighting
brackets, wiring, poles, frangible and safety bases, pads and footings, lowering and
raising devices, sub-stations, distribution assemblies, cabinets and power supplies on a
regular basis.
• Visual inspection and repair of all grounding and bonding connections and terminations
once every 4 to 5 years as part of the relamping cycle. Check that all connections and
terminations are tight; and that wires are not corroded, frayed, or broken.
•
Testing, repair and replacement of faulty components on all Roadway Lighting System
Components including luminaires, lighting brackets, wiring, grounding, poles, pole bases,
Page | 35
May 2015
•
•
•
frangible and safety bases, pads and footings, lowering and raising devices, sub-stations,
distribution assemblies, cabinets and power supplies a minimum of once every 4 years..
Luminaires that are replaced should be replaced with luminaires of similar photometric
performance, or as directed by the asset owner.
Perform ground resistance testing at each power supply ground electrode a minimum of
once every 4 years.
Perform ground resistance testing at each ground grid and ground electrode a minimum
of once every 8 years.
Group replacement of light sources (lamps) in Roadway Lighting Systems on a fixed
cycle according to Table 2.
In addition to the aforementioned Routine Maintenance activities, the following activities should
be completed for all High Mast Lighting Systems:
• Top-latching raising and lowering systems should be inspected, operationally tested, and
maintained at least once every 2 years.
• Non-latching raising and lowering systems should be inspected, operationally tested, and
maintained at least once every 6 months.
Table 3
Recommended Group Replacement Cycle for Light Sources in Roadway Lighting Systems
Light Source
High Pressure Sodium
Metal Halide
Low Pressure Sodium
Induction
Light Emitting Diode
Group Replacement Cycle ( years )
4-5
3-4
3-4
Replacement according to the manufacturer’s recommendations and the
owner’s experience
Replacement according to the manufacturer’s recommendations and the
owner’s experience
3.1.6 ELECTRICAL POWER SUPPLY FOR OTHER F ACILITIES
Some non-LDC power supplies provide power to both Roadway Lighting Systems and other
systems. Where safe and practical to do so, maintenance on the Roadway Lighting Systems
should be performed without de-energizing the other systems.
3.1.7 ROUTINE M AINTENANCE AND INSPECTION REPORTS
Routine Maintenance and Inspection Reports should be completed for all routine maintenance
activities and should contain the following information:
• Date, time and origin of report
• Location of deficiency
• Date and time of arrival at the site
• Weather conditions at the site
• Defects as observed
• Steps taken to rectify the defects and description of repair work completed
• Inspection reports shall include status of the following functions:
o operational status
o Status of all protection equipment – surge protectors, breakers, lightning
arrestors, etc.
o Conditions and status of all hardware, poles, luminaires, etc.
• Status of all grounding and bonding equipment
• Any additional or follow-up work that may be required and the relative urgency of the
follow-up work required and temporary repairs made.
• All reports must contain full details of work performed.
• Date and time repairs were completed
Page | 36
May 2015
3.1.8 NON-ROUTINE M AINTENANCE AND INSPECTION REPORTS
Non-Routine Maintenance and Inspection Reports should be completed for all non-routine
maintenance activities and should contain the following information:
• Date, time and origin of report
• Location of deficiency
• Date and time of arrival at the site
• Weather conditions at the site
• Defects as observed
• Steps taken to rectify the defects and description of repair work completed
• Inspection reports shall include status of the following functions:
o operational status
o Status of all protection equipment – surge protectors, breakers, lightning
arrestors, etc.
o Conditions and status of all hardware, poles, luminaires, etc.
• Status of all grounding and bonding equipment
• Any additional or follow-up work that may be required and the relative urgency of the
follow-up work required and temporary repairs made.
• Note of any police officer’s name and badge number and complete damage report
detailing material and repairs required.
• Record Incident or Motor Vehicle Collision Number if available
• All reports must contain full details of work performed.
• Date and time repairs were completed
3.1.9 EMERGENCY LOCATES
Emergency locates may be required in order to proceed with emergency repairs to protect public
and worker safety and to repair roadway infrastructure or other infrastructure within the roadway
right-of-way (e.g. utilities). Therefore emergency locates should be performed in a timely manner
and with the same dispatch as Non-Routine Maintenance on Critical Failures of the Roadway
Lighting System.
3.1.10 OUTCOME T ARGETS
The Roadway Lighting Systems should be maintained such that the following outcome targets are
met or exceeded:
Feature
Outcome Targets

Roadway
Lighting
System
High Mast
Lighting
System
Page | 37
Response to all Critical Failures in a timely manner from the time of
detection or being made aware of the Critical Failure.
 Permanent or temporary repairs completed or made safe before
leaving the site
 Permanent repairs completed in a timely manner.
 For continuous lighting, the percentage or number of luminaires not
functioning, and the duration of the non-functioning, does not exceed
the limits in the “Minimum Maintenance Standards for Municipal
Highways” (Ontario Regulation 239/02 ).
 For partial lighting, no more than 30% of the luminaires connected to a
power supply not functioning, and no single luminaire not functioning
for more than 14 days from the date of being made aware of, or upon
detection of, the failure.
 Bonding and grounding System Components perform their intended
function and comply with the Ontario Electrical Safety Code in place on
the date of installation.
 Response to all Critical Failures in a timely manner from the time of
detection or being made aware of the Critical Failure.
 Permanent or temporary repairs completed or made safe before
leaving the site
 Permanent repairs completed in a timely manner.
 No more than 25% of the luminaires per high mast lighting pole not
functioning.
 Bonding and grounding System Components perform their intended
function and comply with the Ontario Electrical Safety Code in place on
the date of installation.
May 2015
3.2
TYPICAL LIGHTS-OUT PROCEDURES – TROUBLESHOOTING
•
•
•
•
•
•
•
Disconnect inline fuses for the streetlight luminaire
Test incoming voltage at fuses
Test fuses
Repair luminaire as necessary
Reconnect fuses
Test incoming voltage at luminaire
Secure all ground connections to the pole hand hole, handwell and any other ground connections at
the pole
• Visually establish the integrity of the ground wires, crimps, etc.
For detailed lights out procedures refer to IES DG-4: Design Guide for Roadway Lighting Maintenance
Temporary Repair (Response Maintenance)
1. Response Maintenance is defined as the response to a reported or discovered malfunction of street
light. Prioritize all calls and actions to maintain public safety and convenience. The priorities should
consider all situations such as:
a) Public and personal safety
b) Impact on traffic flow/pattern
c) Location of problem
d) Time of day
e) Scope of remediation (repairs, modification, replacement, etc.)
2. Request help (e.g. journeyman, lineman, policeman) if possible and use the safest method for all
existing conditions.
3. After the work site is secured, the repairperson shall then correct the malfunction of minor nature.
This corrective action shall include, but not be limited to, the activities as follows:
a) Check for contact voltage
b) Check for power and line source
c) Replacement of blown fuses or resetting of circuit breakers
d) Repair or replacement of electrical cabinet
e) Replacement of the malfunctioning photo cell
f) Replacement of the malfunctioning ballast
g) Replacement of the street light fixture
h) Perform load check (as per Section 3.3.4)
i) Check again for contact voltage
j) Ensure site is left safe, with no undue harm potential to the public as per Local and Provincial
Standards
4. For knockdowns (poles, cabinet, etc.), remove facilities if possible to reduce potential damage. Refer
to Emergency Repair Procedure. Coordinate with on-duty police officer at site. Replace unsafe
component or cabinet.
5. If a power outage occurs, the appropriate LDC shall be informed to restore power source.
6. If the damage affects public safety, the repairperson should contact and coordinate with the police to
ensure site safety prior to leaving the site.
The repair person shall record all completed work activities on a work order or similar
documentation
Page | 38
May 2015
Emergency Repair
METHOD AND PROCEDURE:
1. Secure the location according to provincial Work Zone Traffic Control Plan. Coordinate with on-duty
police officer at site. When a police officer is not at site, request the assistance of a police officer if
needed.
2. The repairperson shall inspect the type of emergency, damage, knock down and road condition.
Attachments to knock down pole, e.g. traffic sign, light fixture, mast arm, etc., shall be noted.
3. Prior to the start of any repair work, request appropriate journeyman, lineman, specialist or other help
if needed and use the safest method for all existing conditions.
4. If the damaged pole is a streetlight only pole, perform emergency repair as appropriate; otherwise,
notify the corresponding pole owners. Traffic signal and traffic sign support poles are maintained by
municipal traffic operations department.
5. If the damaged facility carries electrical cables and priority repair is required, inspect the electrical
system. When deficiencies are found, they shall be repaired immediately or make safe for next
working day repair. Make safe any exposed wires and connectors.
6. Remove facilities if possible to reduce potential damage. Clear pole, obstruction and debris from
roadway.
The Repairperson shall record all completed work activities on a work order with Incident or Motor Vehicle
Collision Number if available.
3.3 DETECTION AND TESTING OF CONTACT VOLTAGE
Contact voltage can occur on most types of streetlight installations and can result in the exposure of
pedestrians or their pets to shock, injury or death. Contact voltage is caused by faults in electrical
systems from overheating, corrosion, improper wiring, construction damage, or damage to third party
lines such as LDC lines or seasonal lighting. Workmanship problems may contribute to the underlying
failure. Contact voltage may be present on metal poles, handwells, and access panels as well. Nonmetallic poles can also conduct electricity when wet and an internal fault can deliver a shock through
concrete or rebar. Similarly, sidewalks can become energized by an underground fault in cables or
connections.
The actual voltage detected or measured is not related to the severity or risk of shock posed by the
underlying fault. Published data from New York utility Consolidated Edison demonstrates that voltage
recorded by the utility during investigation of reported, confirmed shocks range from 1-120V and higher,
with many voltages below 5V. These measurements are taken by workers arriving at the scene hours
later or even the following day. This suggests that voltages from high impedance faults do not remain
constant over time, but are functions of environmental conditions, such as temperature and moisture
levels in the soil. Detection of contact voltage is possible using existing technology. Investigation of
findings 1V or greater is recommended to ensure public safety and system reliability. It should be kept in
mind that an effective detection program will typically yield many findings in the 1-10V range. Many of
these findings will be traceable to an electrical fault.
3.3.1 DETECTION OF CONTACT VOLTAGE ON S TREET LIGHTING INFRASTRUCTURE
Contact voltages are detected in three ways.
•
•
•
Direct detection – A managed program of testing streetlights for contact voltage.
Incidental detection – Energized streetlights may be discovered during maintenance work or
through abnormalities noticed during visual inspections.
Reported shock – Streetlight involved in a shock incident reported by the public.
3.3.1 a) Direct Detection
An asset owner or electric utility may positively impact public safety by periodically testing
streetlights for contact voltage. The goal of such a program is to detect energized streetlights (or
other objects) which could indicate electrical faults internally or underground. Once detected,
further steps can be taken to evaluate whether a potential hazard exists and make a decision to
effect a repair. It is advisable to use the most sensitive means available to detect possible faults
and then use a more rigorous measurement process to rule out conditions which do not come
from a fault and therefore are not likely to be hazardous. A very sensitive detection process
accomplishes the goal of proactively finding and repairing faults, preventing contact voltage
incidents, and improving the safety and reliability of the system.
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May 2015
3.3.1b) Incidental detection
Detection of an energized streetlight can also occur
during regularly scheduled repair and maintenance
work. The addition of pre and post-work tests for
contact voltage is recommended for both public and
worker safety. These checks are ideally performed
with a voltmeter against a grounded reference point.
3.3.1c) Reported shock
First responders investigating a reported shock site
should assume a fault condition exists and treat
surfaces as energized until proven otherwise using
actual voltage measurements against verified ground
references.
Figure 13 - SVD 2000 mobile detection
system
3.3.2 DETECTION EQUIPMENT
This guideline is not intended to suggest a requirement
to use a specific technology, but adoption of contact
voltage methods should consider the public safety
ramifications resulting from the limitations of the
method chosen. The most sensitive detection tools on
the market, and the only ones with any significant field
use are the SVD2000, Figure 13 (Power Survey
Company) and the LV-S-5, Figure 14 (HD Electric.)
Voltmeters are used to verify indications from both of
these, and can also be used to check for voltage before
and after regular streetlight maintenance activities.
3.3.2. a) Mobile Electric Field Detection
The SVD2000 is a Mobile Electric Field Detector and
Comparator (MEDAC). MEDAC detection relies on a
capacitive sensor which detects small changes in the
Figure 14 - HD Electric LV-S-5 Low Voltage
ambient electric field caused by the presence of an
Detector
object energized by AC voltage (typically 60Hz). The
sensor operates on a mobile platform, and deviations
from background field levels are readily apparent to a trained technician as the sensor moves
with relation to energized objects. The SVD2000 has been tested by an accredited independent
laboratory for reliable detection of contact voltage in field operating environments. In operation
the system routinely produces detections of street lights energized to as little as 1 volt. It can test
an area quickly, and provides both positive indication of an energized surface, and evidence that
streetlights not giving rise to an electric field indication were not energized at the time of testing.
It simultaneously detects handwell covers and sidewalks energized by failed underground cables.
As of this writing it is used in several cities in the US and Canada and has detected tens of
thousands of streetlights energized by contact voltage. It is the most sensitive detection method
currently available.
MEDAC systems have limitations with respect to streetlight contact voltage detection.
Underground distribution and mixed OH/UG distribution are generally testable, though field levels
from directly overbuilt high voltage lines can mask contact voltage signals in some areas.
3.3.2. b) HD Electric LV-S-5 Low Voltage Detector and “pen testers”
Handheld capacitive or “pen” testers have been used to detect contact voltage. They detect a
potential difference exceeding a pre-set threshold between the sensor tip and the user’s body,
which is assumed to be capacitive coupled to ground. The HD Electric LV-S-5 is the most
sensitive pen tester available. Independent lab tests have documented detection of 5V in a lab
environment, though its sensitivity to contact voltage in the field environment outside the
laboratory has never been independently tested. As of this writing, all other marketed pen
detectors are less sensitive than the LV-S-5 and are not recommended for use in contact voltage
detection. Along with direct voltmeter measurements, the LV-S-5 is one of two methods for
detecting contact voltage directly under primary distribution lines.
Pen testers have limitations as general contact voltage detection tools. The asset list-based
process misses faults in conduit or underground, which may energize sidewalks or other surfaces
Page | 40
May 2015
that do not appear on an asset list. Also, the threshold filters out findings without allowing the
user to determine whether a potential hazard exists. The ground reference (the user) is always in
proximity and sometimes in physical contact with the presumed energized surface, making the
test subject to false negatives. Point measurements provide no evidence that a tested streetlight
(or other surface) can be said to have not been energized at the time of test. Variations from user
to user also affect the reliability of testing with a pen tester and usage practices must be trained
and reinforced for all personnel:
I.
Make solid metal-to-metal contact with each surface tested. Paint can mask energized
surfaces from detection with a contact device.
II.
Test each part of the lamp separately. Metal surfaces in physical contact are not
necessarily in electrical contact, especially if painted or corroded (see Fig 15.)
III.
Grip the detector firmly with a full bare hand, no gloves.
IV.
Hold the detector at arms’ length and test from several angles to reduce the chance of
standing on energized ground.
V.
Test the battery frequently, especially in cold weather.
VI.
Use common sense – do not disturb visibly damaged
wiring or streetlights with
evidence of burning, smoke, or other signs of an active electrical fault.
Figure 15 - Physical contact is not electrical contact. “Pen
tester” must test each part of a lamp separately, e.g. pole,
base, access door, bolt covers, mounting flange
Figure 16 - Digital Voltmeter with low impedance voltage
measurement option built in.
3.3.2 c) Digital Voltmeter (DVM) with Low Impedance Feature (Figure 16)
Digital Voltmeters can be used to detect contact voltage directly. A DVM is always used as a
means of verifying the voltage once it has been detected by whatever means. DVMs are
impractical for large scale contact voltage surveys of streetlighting infrastructure. Each
measurement with a DVM requires three steps:
•
a reliable earth-ground reference point must be established
•
test probes must make solid physical contact with the electrified surface (each part)
•
DVM's are impractical for detecting underground faults
DVM's are therefore only of use in contact voltage detection where testing is done as part of
routine maintenance or where municipal assets are few in number. This does not diminish the
fact that DVM's are a must for verification of a fault which has been detected by a wide area
scanning technology. Always select a DVM with low impedance (LoZ) voltage setting so as to be
able to distinguish real hazards from capacitive coupled voltages. Various manufacturers
including Fluke, Greenlee and Agilent offer DVM's with this feature. Analog voltmeters are also
capable of loading down a circuit sufficiently to eliminate ghost or phantom voltages. For
convenience, it may be preferable to use a meter with a built in feature versus an add-on shunt
resistor.
3.3.3 VERIFICATION AND M EASUREMENT
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May 2015
Figure 17 - Examples of a handheld electric field detectors which can be used to check
ground references for voltage
Detection of a voltage is the first step, followed by an investigation to accomplish the following:
1. Identify a ground reference point to use for a field measurement
2. Eliminate false positive detections due to capacitive coupling
3. Accurately measure the voltage
4. Characterize the source of the voltage
3.3.3.1 I DENTIFY SUITABLE GROUND REFERENCES
A suitable ground reference must not be energized (by the same fault being tested) and must
have low impedance to ground. Ground references available at street level include but are
not limited to fire hydrants, fence or sign posts driven into earth, grounded street furniture,
and temporary grounds driven for the purpose of testing.
General Do’s and Don’ts for selecting ground references:
• Do Carry long ground leads, 15m (50ft) minimum, to easily reach a suitable ground in the
immediate area. Ground leads should have strong spring clamps.
• Do spend extra time making a clean, bare metal contact for your measurement.
• Do verify that ground references are not energized
• Do a proper utility check for underground infrastructure prior to driving a test ground rod.
• Don’t use ground electrode inside or directly adjacent to the light being tested. If lamp
has voltage, the ground electrode will also have some elevated potential to local ground
• Don’t connect to an auxiliary part of a ground reference, such as an operating handle or
knob. The main body is more likely to be solidly grounded.
A handheld electric field detector like the ones pictured in Figure 17 are ideal tools for
verifying a reference is not energized, indicating zero e-field. Otherwise, a voltage test can
be repeated using two or more references. The voltage reading should be the same among
them. If they differ, a reference could be at elevated potential. Pen testers cannot indicate
the absence of a voltage, and are not suitable for verifying ground references.
Re-verifying all voltage measurements against multiple field grounds using the shunt resistor
provides a useful assurance that ground references have low impedance and do not
contribute very large errors to measurement.
3.3.3.2 ELIMINATE CAPACITIVE COUPLING AND OBTAIN ACCURATE, REPEATABLE
MEASUREMENT
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May 2015
Field measurements, especially if the voltage is low, are subject to large errors. Though
surface voltage measurements do not directly correlate with the severity or risk of shock
posed by an underlying electrical problem, it is important to obtain accurate, trustworthy data
about energized surfaces whether they are reported as shock sources or detected as part of
a proactive testing effort. This small extra effort reduces confusion from technician to
technician and among various parties involved with testing, troubleshooting, repair and
general oversight of streetlight testing efforts. It also ensures that field efforts are not wasted
by either pursuing false positive indications or failing to recognize a problem.
Voltage measurement with a shunt resistor eliminates instances of capacitive coupling
(sometimes called “phantom voltage” by electrical tradesmen) from detection results. While
the terms 'ghost' or 'phantom' voltage may not be found in the official IEEE dictionary, they
are nevertheless ubiquitous in the electrical industry. Many articles and papers are available
on the subject. Experienced electricians and technicians learn to recognize and distinguish
ghost voltages from real contact or stray voltage situations. Voltage appears on metal
surfaces due to capacitive coupling and as such generally does not represent a shock
hazard. It is therefore important that professionals who may be conducting a search for
legitimate contact voltages be aware of this phenomenon and be properly equipped with
discriminating instrumentation such as a shunt resistor, digital voltmeter with a low
impedance (Lo-Z) voltage setting or an analogue meter. Once the source is adequately
loaded by the instrumentation, capacitive coupling will drop significantly in magnitude.
Measure the voltage using Lo-Z setting or fitted with a shunt resistor in parallel with the test
leads, as shown in Figure 18. 3000
  shunt resistors can be constructed from easily
available parts or can be purchased from the voltmeter manufacturer. The voltage
measurement will change slightly when the shunt resistor is placed into the circuit, because a
small amount of current is allowed to flow from the energized source to ground. If the voltage
is sourced only from capacitive coupling, no current will flow and the measured voltage will
collapse to zero.
After eliminating findings of capacitive coupled voltage, a few additional measurements will
ensure accurate, repeatable data. Field measurements are dynamic, changing with the
precise measurement point and the pressure applied by the technician. By observing and
minimizing the small change in voltage with the shunt engaged, the technician can minimize
contact and ground impedances and get accurate readings that are repeatable from person
to person. This activity calls for a “pushbutton shunt” (Figure 19) or a resistor that can be
quickly engaged and disengaged without disconnecting or moving the test leads.
3.3.4 CHARACTERIZE CONTACT VOLTAGE SOURCE
Voltage measurement alone cannot distinguish a fault condition from Neutral to Earth Voltage
VOLTMETER
V
ZC1
ZSH
ZC2
ZS
AC
ZS
I
ZC1
ZG
ZC2
ZG
ZSH
SOURCE
IMPEDANCE
CONTACT
IMPEDANCE #1
CONTACT
IMPEDANCE # 2
GROUND
IMPEDANCE
SHUNT
IMPEDANCE
Figure 18 - Measurement circuit of
energized object with shunt resistor in
parallel. Switch represents the pushbutton
capability, which is most helpful for
repeated measurements.
Page | 43
Figure 19 - Pushbutton shunt resistor puts shunt
resistance in parallel with test leads only while
button is engaged, allowing quick measurements
with and without shunt without the need to move
test leads.
May 2015
(NEV), but the voltage source can be characterized to determine the appropriate actions. AC
voltage sources can be one of three types:
rd
a) Phase (or supply) conductor fault- faults in internal wiring, service cable, or 3 party owned
conductors
b) Neutral fault – if neutral is faulty, return current is forced through the grounding of the
streetlight, energizing the pole to a voltage proportional to ZG.
c) Neutral to Earth voltage (NEV) - neutral voltage rise due to return current flowing through the
impedance of the neutral
Phase conductor faults are sourced at line voltage, nominally 120V. Whatever the voltage at the
time of a test, these may become hazardous as the fault deteriorates or environmental conditions
change. Neutral faults, similarly, pose risk of shock if a person or animal becomes a parallel path
to ground for return current. NEV is generally stable, low voltage and presents little to no risk of
shock. Of these three, only NEV is a normally occurring condition which does not accompany
some material fault in cable or connections.
Harmonic analysis can help determine the likely source behind a detected voltage. Equipment is
available from several manufacturers to do this analysis. Non-linear loads, including lighting
ballasts, impose third harmonic (3HD) voltage distortion on neutral return current. Measurements
of >10% 3HD indicate either a neutral fault or NEV. A load test can distinguish a faulty neutral
from NEV because only the faulty neutral will cause a greater than normal voltage drop under
load. A line source is pure 60Hz with <5% 3HD. Consequently, measurements of <5% 3HD
characterize faults in distribution or supply conductors, ahead of the load. When 3HD is between
5% and 10%, the source is less clear and should not be characterized from harmonic analysis
alone. Further hands-on troubleshooting steps will be needed to locate the source, as described
in the next section. Figure 20 shows harmonic analysis output with 2.8% 3HD, indicating the
voltage is sourced by a phase conductor.
Figure 20 - Output screen showing 2.8% harmonic voltage distortion from a
Fluke model 345, one of many tools available for harmonic spectrum analysis.
Page | 44
May 2015
3.3.5 M ITIGATION S TEPS
If harmonic analysis is inconclusive (between 5-10% 3HD,) perform all steps.
<5% Harmonic
1. Test the “hot” and neutral wires for reversed polarity.
2. Unplug or unmake the fuse connection to disconnect lamp feed source. If the elevated
voltage condition goes away, the fault is downstream of the fuse. Check connections and
accessible parts of the streetlight for damage if the source is a phase fault.
3. Check to see if additional sources are connected via overhead cables. If so, de-energize
those one at a time to see if they are the cause of the energized streetlight.
4. If the elevated voltage condition remains on the streetlight pole with the fuse and any other
sources disconnected, the fault is in the underground service conductor or main feeder. Check
for voltage on the service conduit, handwell, sidewalk, or roadway. Disconnect the service at the
feed structure. If voltage remains, there may be a faulty service to a nearby kiosk, building, etc or
faulty secondary running past/under the site. This is a hazardous condition and should not be left
unattended
>10% harmonic
1. Check for neutral faults by performing a load test with dummy load, typically 1000W or more.
If voltage drop is >5%, check neutral connections or cable for possible repair or replacement.
Start at the feed structure and work back towards the supply transformer.
2. If the load test passes and voltage is low, <10V, the source is most likely NEV. Reducing NEV
is best achieved by checking and remaking neutral splices upstream of the energized lamp
starting from the feed structure and working towards the source transformer to reduce the neutral
path impedance. On a long circuit, longer term projects may be required such as increasing the
size of the neutral. An engineering analysis will be required to determine if mitigation is
necessary.
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May 2015
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May 2015
3.4
SAFE LIMITS OF APPROACH
Maximum clearances are given in the chart below with reference to the Ontario Health & Safety Act
(OH&SA) requirements for both personnel and equipment in respect of utilization voltages. Further
information is provided by the Infrastructure Health and Safety Association – IHSA (formerly Electrical &
Utility Safety Association (E&USA)) and by the OH&SA. The worker should consult these relevant
guidelines if not familiar with their content. Also, refer to the requirements as provided in Authority/Utility
standard specifications and/or standard drawings.
Both OH&SA and IHSA provide guidance to assist workers in working safely in close proximity to
electrical wires and equipment and to assist in applying appropriate emergency response measures in the
event of electrical contact. It is the responsibility of the Owner and Contractor to ensure that maintenance
is carried out in a safe manner. Legislation requires that all related hazards are identified ahead of time
and that only competent workers are allowed to work without direct supervision. A competent worker is
defined as a worker who is qualified because of knowledge, training and experience to perform the work,
a worker who is familiar with the OH&SA and with the provisions of the Regulations that apply to the work
and a worker who has knowledge of all potential or actual danger to health or safety in the work being
carried out.
Prior to carrying out any work, a determination on whether hazards exist must be made. This should
include verifying the operating voltage of the overhead and exposed lines. Workers should always
consider the system as being live, having the potential to cause serious injury or death. Contact must be
avoided at all costs. A safe work plan must be developed ahead of time to address all related matters.
Whether or not the worker is a licensed power line worker, the safe limits of approach must be adhered to
and proper PPE and precautions must be taken.
The worker must also consider the age of the system in-so-far-as it may not have been designed with the
clearances below in mind. A worker must be aware of these situations which must be addressed in the
safe work plan.
SAFE LIMITS OF APPROACH
Maintain Maximum Clearances and Install Barriers Where Practical
Mobile Work Equipment *
NonCertified
Isolated
Insulated
O.H.S.A.
O.H.S.A. Authorized Restricted
Booms
A.D.
Minimum
Worker
Zone
Personnel Zones *
Voltages
750V
to 15kV
> 15kV
to 35kV
> 35kV
to 50kV
> 50kV
to 150kV
> 150kV
to 250kV
> 250kV
to 550kV
*
> 0.9m
> 3.0m
> 4.5m
> 6.0m
0.9m to
0.45m
> 0.9m
> 3.0m
> 0.45m
> 1.2m
1.2m to 0.6m
> 1.2m
> 1.5m
1.5m to 0.9m
> 2.4m
> 0.9m
> 2.1m
2.1m to 1.2m
> 3.0m
> 1.2m
> 4.6m
> 2.75m
RBD, Aerial
Ladder,
Work
Platform,
Uncertified
Aerial
Device
Certified
and Tested
by
Certified
Laboratory
3.7m to
2.75m
For detailed information relating to Limits of
Approach Conditions and Restrictions, refer to
Electrical Utility Safety Rule # 129 and trade specific
documentation.
Page | 47
> 0.3m
0.9m to 0.3m
> 3.7m
> 4.5m
> 6.0m
Cranes
Power Shovels
Back Hoes
Mechanical
Brush Cutter
May 2015
3.5 DEVELOPING A CONTACT VOLTAGE DETECTION PROGRAM
This section addresses the typical questions faced by asset managers when developing a contact voltage
detection program. It attempts to look at the subject of contact voltage detection more from a project
management perspective and is presented in a question and answer format. Recommended practices
are written in italics and highlighted.
3.5.1 SHOULD WE DEVELOP A CONTACT VOLTAGE DETECTION (CVD) PROGRAM ?
Contact voltage is a condition that won't go away by simply ignoring it and one which will only
become more prominent as infrastructure ages. It is a serious public safety concern that warrants
serious consideration.
Despite the best preventative efforts being made during design and construction, contact voltage
detection is a valuable part of maintaining a street lighting system.
Due to the nature of a high impedance fault or a failing system neutral, a dangerous voltage can
be present and can remain on a conductive surface which is otherwise properly grounded and
bonded.
In this circumstance, the protective device may not operate to remove the hazard if the fault
current is below the trip threshold. This is analogous to the dangerous condition that exists when
the earth is relied upon to act as a fault current return path.
The occurrence of system faults leading to contact voltage is common, therefore a program of
regularly scheduled CVD is recommended.
While the use of modern ground fault monitoring instrumentation and/or double (Class II)
insulation might reduce the risk, it cannot be eliminated.
Recommendation: each SL Asset owner in Ontario creates a written CVD policy to deal
with the hazard in a proactive manner.
3.5.2 W HAT IS THE MOST EFFECTIVE WAY TO COMBAT CONTACT VOLTAGE HAZARDS ?
The best way to deal with any hazard is to try to prevent it in the first place. In order to reduce the
probability of a future contact voltage incident, asset managers should adopt appropriately
considered guidelines as presented throughout this document.
A comprehensive review should include:
• grounding and bonding practices
• conductor clearances and burial depths
• guarding and mechanical protection
• conductor insulation grades
• connection and splicing methods
• component specifications (poles, luminaires, enclosures etc)
• protective devices (fuses, breakers, GFCI's etc)
• fault monitoring and communications systems
Recommendation: each SL owner in Ontario review its street lighting design and
construction standards with contact voltage prevention in mind.
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May 2015
3.5.3 HOW OFTEN AND EXTENSIVELY SHOULD WE CONDUCT CVD?
Policy on CVD varies greatly across North America. Some asset owners in the USA are required
to test their electrical assets twelve times per year, others test voluntarily, while others do no
testing whatsoever and have no policy in place.
The spectrum of options for CVD is wide and includes:
• Test new installations upon commission.
• One-time audit of existing infrastructure.
• Test only areas of high exposure or high risk.
• Spot checks at trouble-call times.
• Routine tests at re-lamp intervals.
• Testing before and after maintenance work is performed
• Regular testing independent of other maintenance cycles.
(Typically done on a monthly, semi-annual or annual basis).
• performing multiple-asset, wide area mobile patrols
(As opposed to manual, asset specific, foot patrols).
• Any combination of the above
To determine the appropriate approach, standard risk assessment techniques may apply and
start with a comprehensive review of all the relevant data including:
• engineering standards (past and present)
• asset condition assessments
• maintenance intervals and practices
• maintenance records (faults and failures)
• public contact voltage incident reports
• performing an initial detection audit of a portion, if not all of its asset
A few of the key Risk Factors are as follows:
a) Streetlights and other loads supplied from underground infrastructure are more likely to have
buried or concealed faults than overhead systems, where conductors are mostly visible and out of
reach of the public.
b) High Pedestrian/ pet traffic increases exposure to faults, if they are present
c) Conductive raceways/ equipment provide more paths for fault energy to objects or surfaces not
intended to be energized, in the public right of way.
d) Age, environmental conditions, high vehicular traffic, vandalism, and rodents may make some
areas more prone to wear or damage.
Once all the relevant information has been collected and analyzed, some indication of the areas
of greatest concern may begin to emerge. CVD frequency and extent should be reviewed based
on initial and subsequent findings.
Recommendation: Each SL owner in Ontario review their assets and establish their own
standards for CVD on new and existing installations based on the list above.
Note: Incidence of reported shock should not be the sole consideration when evaluating risk for
the purpose of developing a CVD program. Many cases are never reported.
3.5.4 W HAT ELEMENTS SHOULD BE DEVELOPED IN A CVD PROGRAM ?
Where it has been determined that a formal, comprehensive CVD program should be
implemented by SL Asset owners, the following program elements may need to be incorporated:
• a management team or committee
• a policy or mission statement
• a risk management assessment of assets
• written test procedures (for CVD)
• pre-determined acceptance standards (pass/fail criteria)
• test record and data collection forms
• a testing schedule (frequency, areas etc.)
• a test & repair protocol (who does what)
• an incidence reporting form and protocol
• tool and test instrument specifications
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May 2015
•
•
•
•
•
•
•
•
test instrument calibration and inspection records
procedures for barricading hazardous areas (if CV is found)
personal protective equipment requirements
a CV oriented review of engineering practices
updates to existing asset inspection checklists
changes to existing electrical work safety practices
staffing requirements
a budget
3.5.5 W HO WILL DEVELOP AND MANAGE THE PROGRAM ?
Each SLAO should consider forming a team of qualified persons for the purpose of developing a
CVD policy and a project charter. The team may consider coordinating with the owners of other
electrical assets, such as park lighting and traffic signals.
3.5.6 W HO SHOULD PERFORM CONTACT VOLTAGE TESTING?
Persons trained in performing CVD may assist in troubleshooting but must report incidents
immediately and defer repair work to qualified persons.
This policy must apply whether the work is performed by the asset owners staff, by the street
lighting maintenance contractor or by a specialist brought in for the specific purpose of CVD.
Street lighting equipment should be checked both before regular maintenance work is performed,
for worker safety, and after work is performed, for public safety. This will protect against the
possibility of worker induced faults.
Anyone involved in performing CVD or electrical maintenance must be protected from electrical
hazards by a comprehensive program of workplace electrical safety training. CSA Z462 is an
excellent resource for developing such a program.
Should any serious electrical accident occur it must be reported, investigated, corrected, and
documented as per the OESC and related OESC bulletins.
3.5.7 W HAT HAPPENS WHEN WE DISCOVER CONTACT VOLTAGE?
Aside from the standard procedures for securing and evaluating the electrified structure, the
decision to repair or not-to-repair, may appear to present a contentious issue. This is often
connected with the issue of setting an 'acceptable voltage threshold' for energized surfaces.
The best historical data collected to date would indicate the following concepts are valid;
a) The voltage found on an energized surface cannot serve as an indicator of Mean-TimeBetween-Failure, for the equipment.
Any unintentionally energized surface of a street lighting pole or associated electrical
enclosure indicates a possible fault condition. It should be investigated regardless of the
voltage measurement based on section 3.5.3. The root cause may be hazardous or
benign, but voltage measurement alone is insufficient to make that determination.
b) Unintended voltages measured on a surface are not constant over time.
The only reliable conclusion that can be made from the presence of contact voltage (once
NEV and capacitive coupling “aka, phantom voltages” have been eliminated as a cause),
is that on some level, an electrical fault does exist. Many variables contribute to the
voltage that may be discovered at any given time on the surface of faulted equipment.
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May 2015
Appendix 2 contains a more detailed analysis of these variables. Voltage from an active
high impedance fault may rise up to line voltage at any time.
Since contact voltage is not constant, using just a voltage threshold as a guide for
determining the degree of hazard is inadequate. The correct methodology is to find
energized streetlight conditions where they exist, then use the data gathered from
measurement and diagnostics to make decisions about safety and repair activity. Safe
voltage thresholds are used in NEV mitigation or worker protection standards which do
not deal with faulted systems exposed to the general public. Those threshold values are
unsuitable for the issue of CVD.
Recommendation: When a legitimate electrical fault is found to exist, repairs ought
to be effected in a timely manner before the situation deteriorates further, causes
harm or results in the failure of equipment.
No.
3.5.8 SUMMARY OF CONTACT VOLTAGE M ITIGATION S TRATEGIES
Lifecycle Phase
Strategy
Notes
1
Systems Design
Prevention
The specification of equipment, protective devices, insulation,
bonding conductors and system design is the optimal starting
point where CV hazard mitigation should begin.
2
Equipment
Manufacturing
Prevention
Manage the purchasing process to ensure that suppliers
conform to CSA, ISO and other applicable standards.
3
Equipment
Installation
Prevention
Managing construction methods and workmanship provides
an opportunity to avoid creating hazards through training,
supervision and the use of proper tools and materials.
4
Commissioning
Detection
Includes testing and inspecting the new asset. A key
opportunity to detect and correct latent hazards.
5
Operation &
Maintenance
Detection
Effectiveness depends on frequency and technical
methodology. CV testing intervals should coincide with
commissioning, re-lamping and trouble calls. Periodic,
independent wide area auditing is strongly recommended
where warranted by risk analysis.
6
Equipment
Retrofit
Protection/
Fault
Detection
Street lighting poles and power distribution centers could be
retrofitted with various instruments to provide early warning of
possible system faults. Be aware of their limitations and
operational characteristics.
7
Replacement
Predictive
Schedule replacement of aged infrastructure before problems
occur. May include poles, arms, luminaires and power
distribution panels and wiring. Prevention may be more cost
effective in the long run than detection. Both strategies are
recommended.
Corrective
Action
8
Public Awareness
Campaign
Page | 51
Proactive
Prepare a public information bulletin. Coordinate with your
media personnel.
May 2015
3.5.9 CONCLUSION
Contact voltage hazard mitigation is best accomplished by means of a balanced approach which
includes system design, quality control, inspection, testing, risk analysis, life cycle analysis and
infrastructure replacement.
Three essential conclusions can be made:
a) SLAO’s should proactively test street lighting assets for contact voltage.
b) Any CVD program must be scaled and tailored to the needs of the community it serves.
Various technologies and detection strategies may be employed and the asset manager
must understand the limitations and risks of each approach.
c) Elevated voltage conditions found should be remedied in a timely fashion and proper records
maintained.
In the future, collaboration between agencies will hopefully provide more useful data on the
phenomenon of contact voltage which may lead to more accurate modeling of failure modes, risk
assessment methods and decision making protocols to assist asset managers in developing more
effective programs.
4.0
4.1
MANAGEMENT
POLE TESTING
Pole testing is used by some asset managers to assess the remaining life of a wooden pole. If necessary,
further pole decay can be slowed or prevented through the application of treatment. Experience has
shown that an inspection/treatment frequency of 10 years can reduce pole replacements by as much as
6%. This guideline does not cover testing on poles other than wood.
Adding new loads or apparatus to existing poles requires analysis and permission as per the pole owners
requirements. Loading should follow manufacturer’s guidelines.
4.2
CONDITION SURVEYS
Condition surveys can be used to collect detailed information about the as-built status and condition of
the street light system. This information is useful for developing or updating a geographic information
system or asset registry, optimizing maintenance programs or proactively rebuilding aging sections of the
system. Whether or not to complete a condition survey (and at what frequency) should be determined by
the party responsible for the system. A condition survey may also be necessary when ownership of street
light assets is transferred from one party to another.
The method of surveying (i.e. visual from ground, visual from bucket-truck, etc.) will determine the level of
detail that can be attained. Prior to undertaking such a survey, it is recommended that surveyors be
trained to make and record observations that are as objective as possible to ensure consistency of data.
Where subjective judgments are necessary, they should be accompanied by a standardized description
of what constitutes good condition and poor condition. If a condition survey is to be undertaken, some or
all of the factors and components that follow should be considered:
1) Pole
(a) Structural condition
• Have there been any grade changes or washouts?
• Is the pole bent in any way?
• Are there any cracks?
• Is the pole leaning, and if so to what degree?
• Is any rebar exposed (concrete poles)?
• Are there any signs of corrosion including chipped or peeling paint (metal or
concrete poles)?
• Are there any signs of excessive surface wear?
• Is pole footing compromised – nuts/bolts tight
(b) Are there any obstructions preventing access, or potentially damaging encroachments
to the pole that should be cleared (i.e. vegetation, third party structures or signs, etc)?
(c) Hand hole and internal wiring (if applicable)
• Are all access point covers present and properly secured?
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May 2015
(d)
(e)
(f)
(g)
• Is the insulation on any wiring and/or connections in acceptable shape and
rated and approved for the application?
• Are there any missing grounding or bonding connections?
• Are there any obvious signs of electrical faults on the back of the cover plate
(ie. Pitting)?
• Is there fusing present?
Are there any unauthorized third party attachments?
Are there any signs of vandalism, graffiti or pest infestation?
Is contact voltage present?
Collect Pole Label Information – Class, Manufacturer, Age, Number
2) Luminaire support bracket
(a) Is there any loose or missing hardware?
(b) Are clearances being maintained?
(c) Is there any visible damage or corrosion?
3) Luminaire
(a) Is there any loose or missing hardware?
(b) Is the photocell operating correctly (if applicable)?
(c) Is there any dirt or grime which is impacting the effectiveness of the luminaire?
(d) Is there any visible damage or corrosion or sign of pest infestation?
(e) What is the type , wattage, manufacturer, etc? (photo?)
4) Pull-box, handwell or Service Entrance (if applicable)
(a) Structural condition
• Are there any cracks on the cover or frame?
• Is any hardware missing?
• Is there any foreign debris inside the pull-box that could damage the electrical
insulation?
• Are metal parts bonded or grounded (if applicable)?
• Is there any water or ice present?
• Is the Service Entrance secured/ locked?
(b) Electrical components
• Is the cable insulation cracked or brittle?
• Are there any exposed energized connections?
• Is there any evidence of wear or abrasion on the connector or conductor
insulation?
5) Tree trimming
(a) Are any tree branches or other vegetation blocking the path of the light or encroaching
on electrical clearances?
Ultimately, the value gained from condition surveys will depend on the size of the street light system and
the practices of the party responsible for its operation and maintenance. The decision whether or not to
complete a survey and at what frequency should only be made after a thorough review of the costs and
benefits and after a clear understanding of the scope of work is established.
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May 2015
4.3
EXPECTED SERVICE LIFE OF ROADWAY LIGHTING ASSETS
The table below summarizes the expected service life of some typical roadway light elements.
The expected service life numbers are intended to be used for capital planning and asset management
purposes. These numbers are NOT intended to be an estimate of the elements design life or their mean
time between failure.
Electrical Asset
Group
Electrical Asset
Expected Service Life
Supply Control Cabinet and Equipment
Distribution Assembly Cabinet and
Equipment
20 years
20 years
Grounding Components
25 years
Luminaires
HPS Lamps
20 years
4 years (relamping
interval)
30 years ( not
accounting for pole
knockdowns )
30 years
30 years
Power Supplies
Grounding
Conventional
Lighting
Conventional Poles and Footings
Arms and Brackets
Underground Plant ( e.g. ducts, electrical
chambers, cables )
Highmast Lighting
Luminaires
HPS Lamps
Raising and Lowering Equipment ( toplatching system )
Raising and Lowering Equipment ( nonlatching/bottom-latching system )
Highmast poles and footings
Underground Plant
Page | 54
20 years
4 years (relamping
interval)
30 years
20-25 years
40 years
30 years
May 2015
5.0
APPENDICES
APPENDIX 1
IEEE Paper Review: "Grounding of Distributed Low-Voltage Loads: the Street Lighting Systems"
The recent paper entitled "Grounding of Distributed Low-Voltage Loads: the Street Lighting Systems"
published by the Institute of Electrical and Electronics Engineers is highly insightful and relevant to the
topics covered in this set of 'guidelines' and as such is recommended reading.
The paper is co-authored by Parise, Martirano, Mitolo, Baldwin and Panetta. Appearing in a 2010 journal
it summarizes the both the difficulties presented to the street lighting electrical designer by the challenge
of protecting the public from shock hazards, along with many traditional and forward thinking solutions.
In this paper the authors provide a context for the discussion by explaining the differences in grounding
and bonding systems and standards, as found variously around the world. The relative advantages and
disadvantages of these systems are compared.
The limitations of grounding, bonding and traditional overcurrent and ground fault protection schemes are
presented in consideration of the physical nature of typical electrical faults that can occur in street
lighting. This leads the reader to the logical conclusion that ongoing monitoring and maintenance is
critical to protecting the public from contact voltage hazards.
While maintenance and periodic testing are part of the contact voltage mitigation puzzle, the paper also
emphasizes the importance of 'designing' the hazard out of the system from the onset by incorporating:
•
•
•
•
•
•
•
effective grounding and bonding strategies
double insulation (class II)
proper construction specifications
isolation transformers
testing facilities at the power distribution panel
the use of ground fault detection with surge protection
the use of fault monitoring and communications equipment
This paper appears in the Industrial and Commercial Power Systems Technical Conference (I&CPS),
2010 IEEE. It is available @ http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5489893 ISBN 9781-4244-5600-0.
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May 2015
APPENDIX 2
A Hypothetical Contact Voltage
Scenario
Equivalent Circuit
120 VAC
Metal Pole
R1= Exposed
Conductor
Condition
Cover Plate
Faulted
Conductor
R2= Insulation
Leakage
R3= Wire-plate gap
Impedance
R4= Plate-pole
Bond resistance
R5= Metal surface
Contact resistance
R6 = Resistance to
Earth
Voltage on surface
Of metal pole =???
In this example, a partial list of the variables that might affect the voltage impressed upon the surface of a
metal pole where a damaged or leaky conductor is touching the hand hole cover plate is considered:
1) The resistance of leaky insulation as affected by temperature, voids, imbedded metal particles, absorbed
moisture, wear, and damage sustained during installation or damage from pests.
2) The condition of the exposed conductor, which may be oxidized, nicked or open.
3) The contact surface area and pressure between the wire and the pole, or
4) The arc gap distance (if it is an arcing fault)
5) Any moisture or chemicals present on the inside surface of the pole
6) The bond between the cover plate and the pole
7) Outside surface conditions may be affected by oxidation, paint, dirt etc.
8) Daily load cycling: may influence the evolution of the fault characteristics.
The contact area and pressure between the wire and the pole may be affected by original installation
practices, wind loading, road vibration and thermal expansion and contraction. Where arcing or current flow
contributes to further insulation or conductor deterioration the fault may blow open and clear or evolve into a
more solid state. The voltage present at any given time on the surface will be sporadic and as variable and
unpredictable as the interface impedances listed. This would imply that fault current protection schemes
which depend upon minimum code required grounding and bonding methods may not be entirely effective
for high resistance faults and that a program of regular contact voltage auditing is warranted. Furthermore,
contact voltage auditing cannot and will not detect all faulted structures and so emphasis must be placed
upon prevention during engineering and construction phases.
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May 2015
5.1
DEFINITIONS
Contact voltage – Streetlight energized due to faults in internal wiring or underground service cable
Critical Failure means any failure related to the System Components, which causes the improper
operation of, or the failure System Components such that they are operating under substantial Degraded
Performance; or the failure of any System Component that adversely affects the Roadway Lighting
System or impacts on the public safety.
Degraded Performance means the operation of any Roadway Lighting System with less than 100%
performance of the operational System Components.
Electrical Work means any work associated with the installation, maintenance, modification or removal
of electrical equipment including work required for all auxiliary concrete, mechanical, metallic or
associated non-electrical components or equipment.
ESA is an acronym for Electrical Safety Authority, Ontario’s enforcement agency for the OESC.
Ground Reference – Intentionally or unintentionally grounded object not bonded or physically
contacting the streetlight which is used in the field as a ground for the purpose of voltage measurements.
High Mast Lighting System means a Roadway Lighting System where there are three or more
luminaires per pole and the height of the pole exceeds 20 metres.
Neutral-to-Earth Voltage [NEV] – A potential difference between the grounded neutral conductor of
the utility distribution system with respect to earth potential at a specific location. NEV is a small, normally
occurring potential rise resulting from return current flowing through the impedance of the neutral path.
Non-Routine Maintenance means activity required to repair unexpected failure of equipment
components. It requires immediate action and takes precedence over routine maintenance activities for
the duration of the required action.
OESC is an acronym for the Ontario Electrical Safety Code.
Routine Maintenance means preventative maintenance carried out on equipment at specified intervals
and includes, but is not limited to checking, testing, cleaning, tightening, lubricating, etc. of equipment as
well as minor repairs (generally with hand tools and with materials at hand). The purpose of Routine
Maintenance is to ensure that problems are solved before failures occur. Minor maintenance problems
that cannot be corrected “on the spot” shall be logged and scheduled for further follow-up.
Roadway Lighting System means a system of luminaires, poles, sign luminaires, underpass
illumination, cables, power supply equipment, control system and all associated materials required to
provide illumination on a roadway, highway, street, or associated appurtenances on a Municipal or
Provincial right of way.
Shunt resistor – any small load, placed in parallel with the leads of a high impedance digital voltmeter,
used to assess the relative magnitude of the source impedance of an energized streetlight.
System Components means all hardware and software components, devices, parts and materials
included in the Roadway Lighting System.
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May 2015
5.2
ADDITIONAL REFERENCES
Ontario Electrical Safety Code including all appending bulletins issued by the Electrical Safety Authority of
Ontario.
Ontario Regulation 22/04-Electrical Distribution Safety Regulation
Ontario Regulation 22/04-Technical Guideline for Section 7: Approval of plans, drawings and
specifications for installation work
Ontario Regulation 22/04-Technical Guideline for Section 8: Inspection and Approval of Construction
Guideline for Third Party Attachments
CSA Standards pertinent to the Electrical Work.
CSA C22.3 No.7-10
Guide to Municipal Standard Construction MEA Part 6 Street Lighting
IEEE std 142
Kitchener-Wilmot Hydro Streetlight Bus Voltage Drop Calculation
Section 5.4 of Minnesota Streetlight Design manual
Ontario Traffic Manual
Street Lighting Design Manual City of Oshawa
Lighting Reference Guide, Natural Resource Canada.
5.3
OTHER DOCUMENTS FOR INFORMATION PURPOSES
Ontario Regulation 239/02
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Minimum Maintenance Standards for Municipal Highways
May 2015
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