Guide to electrical Network safety for emerGeNcy services PersoNNel

Guide to electrical Network safety for emerGeNcy services PersoNNel
Supplied to Stephanie Rotarangi from Otago Rural Fire Authority on 22 June 2015
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Guide to Electrical Network Safety
for Emergency Services Personnel
THIRD EDITION
issue 1
MAY 2015
Guidance on identifying and controlling the risk of hazards
in incidents that involve any electricity network
HEALTH + SAFETY
ASSET MANAGEMENT
PROFESSIONAL DEVELOPMENT
Supplied to Stephanie Rotarangi from Otago Rural Fire Authority on 22 June 2015
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Guide to Electrical Network Safety for
Emergency Services Personnel
Guidance on identifying and controlling the risk of hazards in incidents that involve
any electricity network
Issued and published by the Electricity Engineers’ Association of New Zealand (Inc.) (EEA).
First published May 1988
Second edition published April 2009
Third edition published May 2015
ISBN: 978-0-473-32447-6
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Copyright
Copyright is owned by the Electricity Engineers’ Association of New Zealand (Inc.), PO Box 5324,
Wellington.
All rights reserved. No part of this work may be reproduced or copied in any form or by any means
(graphic, electronic, or mechanical, including photocopying, recording, taping or information retrieval
systems) without the written permission of the copyright owner.
Disclaimer
This Guide is not a training manual in its own right. Neither is it a set of detailed procedures for
emergency service response to incidents that involve electrical hazards. It does provide information
suitable for emergency services or training providers to develop policy, detailed procedures, or
training.
This Guide applies to identifying and controlling the risk of electrical and mechanical hazards in
incidents that involve any electricity network. It does not address the scope of non-electrical hazards
that may exist at such incidents, for example environmental or traffic hazards. Emergency services
should use the information in this Guide in managing electrical hazards at incidents. This should be as
part of the broader scope of their hazard management and training of emergency service personnel.
This Guide is recommended as good practice by electricity supply industry representatives, but it is
not a substitute for legislative or other regulatory requirements. If there is uncertainty on what
guidelines or legislative requirements should apply in any particular situation, specialist advice,
including legal advice, should be sought.
The Electricity Engineers’ Association of New Zealand (Inc.) and the electricity supply industry
representatives involved in preparing this Guide, accept no liability or responsibility for an error or
omission contained in this Guide, or any injury, loss, damage (including indirect or consequential loss
or damage), or any other claim from any reliance on, or failure to rely on, the contents of this Guide.
This Guide has been prepared on the basis that the user will be appropriately trained, qualified,
authorised and competent.
Acknowledgements
The EEA would like to thank the organisations who participated on the group that revised this Guide.
The group included representatives from the NZ Fire Service, NZ Police, Ambulance New Zealand
(represented by Order of St John), and electricity transmission (Transpower), generation (Genesis),
contracting (Northpower) and distribution businesses (Vector, Electra and Powerco). The EEA would
like to thank these parties for their participation.
The Electricity Networks Association (ENA) has kindly allowed us to include a link to its website in this
Guide to a map showing the geographic coverage of New Zealand’s electricity network companies.
ii
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Guide to Electrical Network Safety for Emergency Services Personnel
The EEA would also like to thank the Ministry of Civil Defence and Emergency Management for the
use of information and figure from the New Zealand Co-ordinated Incident Management System
(CIMS) 2014 edition.
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Introduction
Emergencies can potentially involve any electricity networks found anywhere in
New Zealand. Electrical and mechanical hazards may arise, for example, from an
overhead line that falls down in a storm or from a motor vehicle or fire incident
that involves electrical equipment. Occasionally, an unauthorised person enters a
substation, or climbs an electricity network pole or tower, risking serious harm or
death. Or a DIY householder may need rescue from a livened metal roof.
Emergency services personnel who respond to such incidents can expose
themselves to the electrical hazards. This Guide helps emergency services
personnel to understand and avoid these.
This Guide provides information about:
•
The electricity supply industry;
•
The fundamentals of electricity and electrical distribution;
•
Effect of electric current through the human body;
•
The different types of electrical equipment;
•
Responding to incidents where there are electrical hazards, and recognising
and avoiding these;
•
Specific, more common incidents;
•
Working with electricity generation, transmission, distribution, and
contracting companies (electricity supply industry, ESI).
Reactive maintenance work and first aid response is outside the scope of this
Guide.
Four key steps for emergency services (LIVE)
In preparing this Guide four key steps were identified for emergency services to
follow when avoiding and controlling hazards from electrical networks. These four
key steps are as follows.
1. Location of incident and assets involved
2. Identification of hazards from electricity network
3. View from at least 4 metres distance (and 8 metres for the public)
4. ESI clearance needed before approaching incident site
This Guide supports training, policy and procedures development; however,
emergency service personnel may also use it in the field. The Appendices
contain essential prompts such as check lists and flow diagrams suitable for field
use.
The content of this report will be monitored and revised periodically. Suggestions
for changes should be sent to [email protected] or Guide to Electrical Network
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Guide to Electrical Network Safety for Emergency Services Personnel
Safety for Emergency Services Personnel, Electricity Engineers’ Association,
PO Box 5324, Wellington, 6145. www.eea.co.nz
Peter Berry
Executive Director
Electricity Engineers’ Association
May 2015
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Contents
Copyright .................................................................................................................................................. ii
Disclaimer ................................................................................................................................................. ii
Acknowledgements .................................................................................................................................. ii
Introduction .............................................................................................................................................. iv
1
Terminology and definitions .............................................................................................................1
2
The electricity industry......................................................................................................................3
3
4
5
6
vi
2.1
Generation and transmission .................................................................................................3
2.2
Local electricity distribution ....................................................................................................4
2.3
Electricity supply to residential and commercial customers ..................................................4
Electricity: the fundamentals ............................................................................................................5
3.1
Voltage ...................................................................................................................................5
3.2
Path to earth and between conductors ..................................................................................6
3.3
Arcing .....................................................................................................................................7
3.4
Insulators and conductors ......................................................................................................8
3.5
Electricity on the ground ........................................................................................................9
3.6
Step and touch voltages in the ground ................................................................................10
Electricity and the body ..................................................................................................................12
4.1
Effect of electric current on the body ...................................................................................12
4.2
Electrical injuries ..................................................................................................................12
4.3
Responding to victims of electric shock ...............................................................................13
Recognising parts of electrical networks ........................................................................................13
5.1
Overhead lines .....................................................................................................................13
5.2
Underground cables .............................................................................................................13
5.3
Ground-mounted distribution equipment .............................................................................14
5.4
Substations ..........................................................................................................................14
Managing electrical hazards ..........................................................................................................15
6.1
What part of an electricity network is it? ..............................................................................15
6.2
Who owns or controls it? ......................................................................................................15
6.3
What voltage is the equipment? ...........................................................................................16
6.4
Is the equipment live? ..........................................................................................................17
6.5
Fire .......................................................................................................................................18
6.6
Minimum approach distances ..............................................................................................19
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7
Managing mechanical hazards ......................................................................................................19
8
Responding where electrical hazards are present .........................................................................21
9
8.1
Communicating with the electricity supply industry .............................................................21
8.2
Arriving on-site .....................................................................................................................22
8.3
The site hazard assessment ................................................................................................23
8.4
Approach distances..............................................................................................................24
8.5
Managing an incident site ....................................................................................................24
Guidance for common incidents .....................................................................................................25
9.1
Victim at house building or factory involving live overhead lines or electrical equipment ...25
9.2
Overhead line brought down by storm or fallen tree ............................................................26
9.3
Vehicle into pole – overhead line down but not on vehicle ..................................................26
9.4
Vehicle into and contacting pole overhead line or other electrical equipment .....................26
9.5
Machinery contacting overhead lines or underground cables .............................................30
9.6
Person on overhead line pole or tower ................................................................................31
9.7
Person in substation.............................................................................................................31
9.8
Fire under or near an overhead line.....................................................................................32
9.9
Fire in a substation ...............................................................................................................33
9.10 Floods ..................................................................................................................................34
9.11 Storms ..................................................................................................................................34
9.12 Other incidents .....................................................................................................................35
9.13 Additional considerations .....................................................................................................35
Appendix A
Identification of electricity supply industry equipment ....................................................36
Appendix B
Electrical hazards – key points checklist ........................................................................42
Appendix C
Pre-agreed communication plans ...................................................................................43
Appendix D
Brief response procedure ...............................................................................................44
Appendix E
Basic knowledge for emergency services personnel on incidents involving electrical
hazards ...........................................................................................................................45
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1 Terminology and definitions
Terms used in this Guide have the following definitions.
Arc (arcing, flashover)
Electric current jumping across an air gap, usually with a bright flash
and a loud noise. A short circuit often involves arc or flashover.
Conductor (conductive)
Any item or substance carrying or transferring a flow of electric
current. Any item or substance is conductive if it has the capacity to
carry or transfer electric current.
Control room
Electricity network centre for controlling the electricity network,
staffed by operators.
Distribution substation
A small substation forming part of a distribution network with an
incoming voltage of 22 kV, 11 kV or 6.6 kV and outgoing voltage of
230/400 V (typically), often referred to as a transformer. These are
overhead on poles, or at ground level, often at road sides.
Electrical equipment
Includes transformers, switchgear, streetlights, industrial and
domestic wiring, appliances and electrical machines and fittings:
Electricity network
Electricity network
company
1.
Transmission equipment refers to any electrical equipment in
the transmission network – the National Grid.
2.
Distribution equipment refers to any electrical equipment in a
distribution network.
A generic term for electricity transmission and distribution systems,
comprising the electrical equipment, overhead lines, and
underground cables that make up the system:
1.
Transmission network: refers specifically to the transmission
system (National Grid), supplying electricity to large industrial
users or to electricity distribution companies.
2.
Distribution network: refers specifically to the distribution
system, supplying electricity for electricity retailers to end-users
such as homes and businesses.
An enterprise owning or managing an electricity network.
For example, Transpower owns the transmission network (the
National Grid), and many power companies own distribution
networks.
NOTE: Different companies (including contracting companies) may
manage, operate, or maintain any electricity network.
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Emergency services
personnel or person
Police, Ambulance or Fire Service workers who attend emergency
scenes or events commonly referred to in this Guide as ‘incidents’.
Emergency services
response work
Work at an accident/incident site in order for emergency services
personnel to rescue victims or to minimise risk of harm to people or
significant property damage due to hazards caused by the failure of,
or damage to, electricity network assets or other installations.
Electricity supply industry
(ESI)
Comprises electricity generation, transmission, distribution, and
contracting and generation companies.
kV
Kilovolt (one thousand volts)
Incident controller
The person who coordinates and directs the response to a particular
incident.
Incident control point (ICP)
A single location where an incident controller and members of their
incident management team (IMT) coordinate and manage response
operations at an incident level response.
Insulating, insulated,
insulator
Preventing conduction of electricity, an object having the capacity to
prevent conduction. An insulator prevents electrical leakage.
Live
Charged with voltage. Usually also means connected to the
electricity network.
MAD
Minimum approach distance (to a live object).
National grid
The transmission network owned by Transpower.
Overhead line
Any overhead electric conductor, including any ‘transmission line’ or
any ‘distribution line’, and including any overhead service
connection to customer property, used for supplying of electricity:
1.
Distribution line: an overhead line usually having voltage
33 kV or less and that forms part of a ‘distribution network’.
NOTE: Some distribution networks include a small number of overhead
lines at voltages 50 to 110 kV. See Table 1 ‘Voltage hazard controls’ for the
hazard control particular to this voltage range: ‘do not approach’.
2.
Pillar (or plinth)
2
Transmission line: an overhead line having voltage that
ranges from 50 kV and up to 400 kV AC and 350 kV DC and
that forms part of the ‘transmission network’ – the national grid.
A connection point between the distribution network and a
customer’s underground electricity service (supply). A pillar stands
about 600 mm above ground. Most commonly coloured black or
green and made of composite material.
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Pit
A connection point between the distribution network and a
customer’s underground electricity service (supply). Found
underground and accessed by a small in-ground lid. Most commonly
coloured green.
Reactive maintenance work
Work to repair damaged electricity supply industry assets after an
incident. This is not covered in this Guide.
Short circuit
Electricity taking a short-cut, for example from an overhead line or
any other electrical equipment to the ground, instead of flowing
normally as intended. Sometimes the short-cut can involve a large
flow of electric current that should automatically disconnect the
electrical equipment, but such disconnection does not always
happen even if designed to do so.
Step voltage
A voltage in the ground that can appear between two points of
contact on the ground.
Switchgear
Equipment used to control (turn on and off) the flow of electricity to
specific parts of any electricity network.
Touch voltage
The voltage existing between a live object and the earth
experienced, for example, touching the live object by hand while the
feet are on the ground.
Transmission substation
A large substation generally owned by Transpower, which may
supply a large industrial customer, a region or a town.
Voltage (volt)
A measure of electrical ‘pressure’: measured in hundreds of volts, or
at high voltage, in thousands of volts (kilovolts – kV).
Zone substation
A major distribution substation that supplies a town, suburb or city
area, typically with an incoming voltage of 66 kV or 33 kV and an
outgoing voltage of 11 kV.
2 The electricity industry
2.1
Generation and transmission
Power generating plants produce electricity at high voltages, typically 50 kV to
220 kV. Transmission lines carry this long-distance to transmission substations in
cities or near certain large industrial plants. Transmission substations reduce the
voltage to between 11 kV and 33 kV. The transmission lines and transmission
substations form the transmission network known as the National Grid are owned
by Transpower.
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2.2
Local electricity distribution
From the transmission substations, the local electricity network company
distributes electricity for the electricity retailers to commercial and residential
customers. The electricity is usually first transferred by overhead lines or
underground cables to zone substations.
Zone substations reduce the voltage to 22 kV or 11 kV and then distribute the
electricity by other overhead lines and underground cables to distribution
substations (sometimes known as transformers).
The distribution substation further reduces the voltage to 400 V and 230 V for
domestic and commercial use. Distribution substations are on the ground or
overhead, on a power pole for example.
The zone substations, distribution substations, connecting overhead lines on pole
or other structures, and underground cables up to the customer connections,
form the distribution networks. There are many distribution networks in New
Zealand.
2.3
Electricity supply to residential and commercial customers
The distribution electricity network connects to customers by either an overhead
line or underground cable. Customer connections are either overhead or
underground ‘service lines’, ‘service mains’ or ‘service connections’. Network
PITs or Pillars supply underground service connections to meter boxes.
Overhead service connections run direct from the street pole to the bargeboard
or another high point on the house, and then by internal wiring cable to the meter
box and switchboard.
Residential customer supply is normally 230 V. Commercial customer supply
voltage varies according to customer needs. Those having high voltage
connection (typically up to 11kV) may have a distribution substation (transformer)
on their property, typically on an external wall or basement, for example a car
park.
Figure 1 represents different components of the electricity supply industry. A map
showing the geographic coverage of New Zealand’s electricity supply industry is
available on the ENA website www.electricity.org.nz.
Note that each connection will include a means of isolation such as a fuse by
which the supply of electricity to the premises may be controlled.
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Figure 1: Electricity supply
3 Electricity: the fundamentals
3.1
Voltage
In its simplest form, electricity is electrical energy transferred by electrical current,
as billions of electrons flowing around a circuit at the speed of light, at a voltage.
Voltage is the electrical pressure or driving force behind this flow. The higher the
voltage, the greater the electrical hazard.
Voltage measure is in volts (V) or thousands of volts (kV). Even a 230 V
domestic electricity supply voltage can kill in certain circumstances, but ‘high
voltages’, 1000 volts (1 kV) or more, are particularly dangerous (See Figure 2.)
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Figure 2: High and low voltages are like high and low pressure water pipes. Both high
and low voltages can kill. ‘The higher the volts, the higher the jolts’
3.2
Path to earth and between conductors
Electric current driven at some voltage with respect to earth has a strong
tendency to leak or short circuit to ‘earth’ – the ground – by any available
conductive material when circumstances allow. This is true regardless of the
source, for example whether the electricity comes from a household lighting
circuit, an overhead line, or lightning.
The tendency for electric current to leak to earth creates one of the major
hazards for emergency services personnel working at any incident involving live
electrical equipment. Any person who directly or indirectly contacts live electrical
equipment or any other live conductive item and the ground at the same time
may form an electrical path to ‘earth’. This could cause death or serious harm.
Examples include a person standing on the ground, touching a vehicle, ladder or
wire fence in contact with a downed live overhead line, or contacting a live
electrical wall fitting while standing in a pool of water. (See Figure 3.)
Another major hazard exists where any person, including anything conductive
that they are holding, bridges conductors that form part of any overhead line or
any electrical equipment that is live, even if the person is insulated from the
ground at the time. This is known as ‘phase’ to ‘phase’ contact. This contact path
can cause comparatively greater electric shock effect than the path to earth for
similar equipment, but both will kill.
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Why is a bird sitting on a live overhead line not electrocuted? Because there is
no path created to earth or to any other overhead line. However if the bird
contacts more than one bare conductor at the same time it will be electrocuted
instantly.
Figure 3: Electric current always looks for the easiest path to
earth – make sure it is not through you
3.3
Arcing
High voltage electric current can also ‘arc’ – jump across an air gap – to create a
path to earth or to any other item of electrical equipment such as an overhead
line. An arc can also jump between conductors in an overhead line or between
live parts of any electrical equipment. The higher the voltage the further the
electric current can arc. A lightning strike is an extreme example of an arc and
involves millions of volts. By contrast, an electric arc-welder works at
comparatively few volts, but the heat produced by the high current is still strong
enough to melt steel.
Common high voltage electrical equipment can produce arcs ranging from a few
centimetres to a couple of metres or more depending on the voltage. For
example, an arc can jump from a high voltage overhead line to any number of
objects to try to create a path to earth, including trees, water, metal objects, a
person or an object a person may be holding. (See Figure 4.)
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An arc (also known in the electricity industry as a flashover) is extremely hot and
can ignite flammable material nearby. Molten metal may also drip or spray into
flammable material nearby such as dry grass, starting a fire.
Figure 4: High voltage electric current can arc across air gaps – Keep well away
3.4
Insulators and conductors
It is important to know that electric current can pass through some materials;
these are conductors. However other materials hinder electric current. These are
insulators, used to prevent electrical leakage.
Examples of conductors include:
8
•
Metals (for example overhead lines, car bodies, fences, roofing, pipes, wires
in buildings, ladders (including ladders with wire reinforcement), wire
fences);
•
Water;
•
Wet wood (including growing trees);
•
People and animals;
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•
Pole structures such as wood poles and concrete poles even if they appear
dry, and steel pole structures;
•
Soil;
•
Flames, hot gases and dense smoke from fires.
A live overhead line lying on something conductive transfers its voltage to the
conductor. For example, a live overhead line touching a car makes the whole car
body live. A car on top of exposed wires in a broken pillar makes the whole car
body live. A live overhead line contacting a phone line makes the phone line live.
Metal and wire reinforced ladders readily conduct electric current. Do not use
these ladders close to live electrical equipment.
Examples of insulators (when clean and dry) include:
•
Glass;
•
Dry wood;
•
Plastic;
•
Porcelain;
•
Rubber;
•
Air.
Some insulating materials such as wood or rubber can become conductors when
wet, contaminated or damaged.
3.5
Electricity on the ground
Electric current can travel through or on the surface of the ground. Current
leaking into the ground surface, for example from a live overhead line on the
ground or from the line contacting a tree or metal fence, will spread out from the
points of ground-contact. This creates a voltage gradient on the surface.
As the electric current spreads out, there is a ‘rippling effect’ on the voltage. The
‘ripples’ created become smaller and smaller as they move away from the point
of contact; that is, full voltage at the point of contact, voltage progressively
reducing with increasing distance from this point. (See Figure 5.)
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Figure 5: A broken overhead line or damaged electrical equipment can cause electric current to
spread out on the ground surface, reducing as it spreads away from the point of contact
3.6
Step and touch voltages in the ground
The voltage in the ground creates two electrical hazards known as ‘step voltage’
and ‘touch voltage’.
a) Step voltage
If there is a voltage gradient or difference on the ground and inadequate
insulation underfoot, electric current will flow through a person’s body from one
foot to the other. (See Figure 6). The illustration shows one foot on the ground at
a point having x volts and the other foot a step away at a point having y volts.
The voltage difference (x-y volts) determines the current level through the body.
This is step voltage.
b) Touch voltage
Touching something live by hand, with feet on the ground, allows electric current
flow through the body to ground. An example is touching a live overhead line or
other live object such as a tree or car in contact with the line. (See Figure 7.)
Vegetation such as trees can readily conduct electric current to ground level, and
dangerous step and touch voltages may be present on the tree trunk and the
surrounding ground.
Be aware that water and conductive objects can extend the step and touch
voltage hazard area. Avoid standing in water or touching metal or conductive
objects near any damaged overhead line or other electrical equipment as any of
these might be live. (See Figure 8.)
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Figure 6: When electric current leaks into the ground dangerous voltages
can occur on the ground surface
Figure 7: Touching anything live may make you a path to earth
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Figure 8: Live overhead lines touching and livening other objects
increase the step and touch voltage area
4 Electricity and the body
4.1
Effect of electric current on the body
The effect that electric current has on the body can vary depending on:
•
the voltage;
•
where the electric current enters and exits the body;
•
the time in contact with the electricity source;
•
the condition of the skin (the severity of an electric shock can be greater if
the skin is moist since the electric current is greater).
A person contacting anything live may be thrown clear, or may become ‘locked
on’ when their muscles tighten from the current flow through the body.
4.2
Electrical injuries
Contact with a live conductor may cause serious external and internal burns,
serious internal organ damage and heart fibrillation. Also a person close to a
large electrical arc may suffer serious burns from the heat and ultraviolet rays.
Ultraviolet rays may also cause flash burns to the eyes in the same way as an
electric welder.
Any person receiving an electric shock that causes any external burns, any
incapacity or any other symptoms, such as those above, must have urgent
medical attention.
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4.3
Responding to victims of electric shock
First check to ensure your own personal safety before aiding any victim. Assess
and manage the electrical hazards as outlined in sections 6 to 8 of this Guide.
A victim may have external burns, their heart may begin to fibrillate, they may
become unconscious, or a combination of these. Contact the relevant emergency
service for assistance. First aid response information is beyond the scope of this
Guide.
5 Recognising parts of electrical networks
It is important to accurately describe to the control room the parts of any
electrical network involved in an incident. The following outlines key recognition
features. Photographs are at Appendix A.
5.1
Overhead lines
5.1.1
5.1.2
5.2
Transmission lines (national grid)
•
Usually found on private property, have Transpower signs, including voltage
information, on the supporting poles and steel towers;
•
Poles made of wood, concrete, or tubular steel section; usually
distinguishable by their large size, having a height range typically
15 – 50 m;
•
Towers usually spread well apart, with conductor spans often greater than
250 m, the conductors held by large insulators usually 1 m or longer.
Distribution lines
•
Usually found along roadsides or on private property;
•
Poles typically timber, concrete; or steel rails usually about 10 m high;
•
Often feature several crossarm layers of overhead lines; small insulators
(<300 mm long) usually pointing upwards;
•
May also carry telecommunications lines;
•
Some poles also support pole-mounted electrical equipment, such as a
distribution substation (transformer) or switchgear.
Underground cables
Underground cables are common with these features:
•
Vary in size from 5 mm to over 100 mm in diameter;
•
Most commonly carry voltage ranging from 240/400 V to 11 kV, and
sometimes up to 66 kV;
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5.3
•
Cables usually laid 600 mm to 1500 mm deep. Changes to ground cover
can alter the depth;
•
Cable risers are often visible above ground entry or exit points, fixed to
wood or concrete poles, or fixed to walls near electrical panels.
Ground-mounted distribution equipment
Ground-mounted distribution equipment is usually found on roadsides or on
private property and includes:
5.4
•
Distribution substations, commonly referred to as transformers, which
increase or decrease voltage;
•
Switchgear, used to control the flow of electricity to any part of a distribution
network;
•
Pillars, which are connection points between the distribution network and a
customer’s underground electricity service.
Substations
The transmission network includes transmission substations. Distribution
networks include many zone substations and many distribution substations.
5.4.1
5.4.2
5.4.3
14
Transmission substations (generally owned by Transpower)
•
In large enclosed outdoor yards;
•
Distinguishable by Transpower signage on the security enclosures or
buildings;
•
Full security fencing and locked gates form the enclosures;
•
The electrical equipment is usually large, mounted on concrete pads, and
connected by overhead lines and cylindrical or bar conductors;
•
Often include one or more buildings, the larger substations including spaces
for indoor switchgear, maintenance workshops and control rooms.
Zone substations
•
Found outdoors, on industrial sites, or in high-rise commercial areas and
sometimes found within a building to blend into the environment;
•
Some outdoor zone substations look like transmission substations but are
smaller.
Distribution transformers
•
Common, found everywhere, typically at or near city, suburb or industrial
area roadsides, as well as in country locations;
•
Most commonly ground-mounted or pole-mounted;
•
Transformers often painted green to blend with the background;
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•
Can also be within buildings.
•
Can also be under hardened plastic or fibreglass canopies.
Substations involve significant electrical hazards. Emergency services personnel
should never try to enter any substation unless a representative of the network
company is present and available to supervise any movements by the personnel.
6 Managing electrical hazards
On arrival at an incident it is important to identify any electrical hazards.
Emergency services personnel including anything you may be holding (for
example, ladders or any hand-held equipment) or anything you may use (for
example, pressurised water or other extinguishment) must keep a safe distance
away from any part of any electricity network involved, including anything in
contact, until they understand the hazards. Voltage from any source can
seriously harm or kill.
Understanding the part of the electricity network involved, what the voltage is,
whether it is live or might be live, is critical to assessing electrical hazards and
deciding how to avoid these. Recognising the part and describing it to the
electricity network control room helps the emergency services personnel on-site
and the electricity supply industry representative(s) to carry out proper hazard
control.
Any particular part of the electricity network involved with an incident can be
treated as being free of electrical hazards only when the authorised electricity
supply industry representative has formally advised that it is safe to do so.
Otherwise, treat the part as being live.
In general, incidents involving electricity networks more commonly involve
roadside distribution lines or ground-mounted distribution equipment.
Emergency services personnel should also be aware that there could be
additional electrical hazards present such as customer-owned generation,
including solar photovoltaic, wind power, micro-hydro, and diesel generators; and
also that power lines can be overheard or underground.
See Appendix B for an electrical hazards checklist to help you address key
aspects of an incident with a potential electrical hazard.
6.1
What part of an electricity network is it?
Section 5 and Appendix A aid in identifying parts of the electricity network.
6.2
Who owns or controls it?
A primary step is to identify the electricity supply industry company that owns or
controls the particular electricity network involved in the incident:
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•
Transmission network poles, towers and substations are clearly identifiable
as belonging to Transpower. Signs will include the line or substation name
and pole or tower number. (See sign example at Figure A.2 of Appendix A.)
•
Distribution network zone substations are often clearly signed with the
electricity supply industry company name and, usually, a contact number.
•
Signage is unlikely on distribution electrical equipment, such as pillars, and
distribution substations (transformers), although some equipment has an
identification number. Some poles are numbered. (See example at
Figure A.2 of Appendix A.)
NOTES:
1. Multiple companies may own, manage, or operate any item of electrical equipment.
For instance, the electricity supply industry representative who arrives on-site may be
an employee of a contractor to the electricity supply industry company.
2. Information on which electricity supply industry or company owns a particular asset,
may be available through the Fire or Police Communications Centres.
3. For information on how to communicate with the appropriate electricity supply
industry organisation see 8.1.
6.3
What voltage is the equipment?
Signs on transmission network poles and towers show the transmission line
voltages. (See example at Figure A.4 of Appendix A.)
Distribution equipment signage does not usually show the specific voltage, but
may show ‘high’ or ‘low’ voltage. The electricity network control room might be
able to advise the specific voltages involved on receiving a description from the
incident site. But confirmation of this may depend on an electricity supply industry
representative arriving on-site.
Table 1 shows the hazard controls likely to suit the voltages once confirmed.
Regardless of the hazard controls applied, remember that contact with any live
electrical equipment at any voltage can seriously harm or kill.
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Table 1: Voltage hazard controls
Voltage
Location/use
Hazard control
230V/400 V
Domestic, commercial, building wiring
and customer-owned generation
Disconnect by switching or
unplugging where possible
230V/400 V
Distribution equipment and distribution
lines: mainly found near roads, in towns
and rural areas and some larger
customer-owned generation (But see
note)
Special tooling and techniques
required
Transmission network including
transmission lines (Transpower’s
National Grid): mainly found on private
property
Do not approach
11,000 V (11 kV)
22,000 (22 kV)
33,000 (33 kV)
50,000 (50 kV) and above
NOTES:
1.
Some distribution networks include instances of overhead lines and electrical equipment at transmissionlevel voltages 50 to 110 kV; hazard controls for these particular items are as for transmission networks and
transmission lines – ‘do not approach’.
2.
Be aware that voltages from customer owned generation (e.g. photovoltaic cells) vary.
6.4
Is the equipment live?
It is impossible to determine whether any electrical equipment or overhead line is
live merely by its appearance. Treat all of these as being live until the electricity
supply industry representative formally confirms that they can be treated as being
free from electrical hazards. The electricity supply industry representative will
usually have to test the equipment to confirm this.
6.4.1
Fallen overhead lines
When any overhead line falls and contacts the ground, the supply of electricity
may automatically be switched off, or the fallen lines may remain live. In
particular, any fallen overhead line will not automatically have its supply of
electricity removed but will remain live where:
•
It is still clear of the ground; or where
•
It is lying on something that is a poor conductor. This could include, for
example, dry concrete or tarmac, ice or snow, dry soil, dead tree, car with
rubber tyres.
An overhead line that has had its supply of electricity removed can also reliven
without any warning. This can happen when switchgear automatically recloses.
Or a control room operator who is not aware of any incident may operate
switches to restore the electricity supply.
It is important to remember that electricity often supplies electrical equipment or
overhead lines from more than one direction, for example livening both ends of a
broken overhead line.
A live fallen overhead line may not necessarily show any sign that it is still live,
but sometimes there might be signs such as:
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•
Sparking or glowing;
•
Crackling or buzzing;
•
Heat or melting;
•
Smoke or steam.
Also, any electrical equipment or any overhead line may still be live if lights or
other electrical items nearby are still working.
6.4.2
Ground-mounted distribution equipment
Vehicles may crash into roadside distribution equipment such as plinths, pillars
and transformers, exposing live parts. This may liven the vehicle, and the live
contact may not be obvious where the vehicle is on top of the roadside
equipment. Also, moving the vehicle while it is in contact with such equipment
may cause it to become livened, if not already so. Treat all vehicles in contact
with such electrical equipment as being live.
6.4.3
Transmission or zone substations
Parts or all of any transmission or distribution substation equipment are likely to
remain live after any incident such as vehicle crash into the equipment. Also,
electricity may supply the equipment from many directions. It is impossible to
assess by mere observation whether the equipment or any part of it is still live,
and therefore it must be treated as live. Any audible hum signals that it definitely
is still live.
6.5
Fire
Fire near electrical equipment presents many hazards. For example, fire can
create dense smoke and hot gas, both of which can conduct electric current. This
increases the likelihood of electric arc from overhead lines to ground, creating
significant hazard to any emergency services personnel trying to put out the fire.
Dense smoke can also obscure the presence of the live electrical equipment.
Water conducts electric current well, and hoses trained on a fire can create a
direct or indirect conductive pathway from the electrical equipment. Electric
current may also arc to ground by the water and hose.
Also, the likelihood of electric arcing is much higher around transmission lines
110 kV or higher.
Trees can also conduct electric current. They can cause electric arc or vegetation
fire if they contact live overhead lines or electric equipment.
Substation fire is particularly dangerous; a pre-agreed fire plan should be
developed with the electricity supply industry company. See 9.9.
Any property fire that involves live electrical equipment in or near the property
creates similar hazards for firefighters.
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These hazards emphasise the importance of keeping fire extinguishment such as
water from any fire hose or any other conductive extinguishment agent a safe
distance from any fire, until confirmed that the property or equipment involved is
free from electrical hazards.
6.6
Minimum approach distances
All emergency services personnel must conform to the 4 metre MAD from any
electrical equipment. Any emergency service persons may approach closer than
the MAD only when the electricity supply industry representative has formally
confirmed that the electrical equipment is safe to approach. If other risks exist, in
addition to electrical risks (such as an explosion risk), the incident controller may
consider imposing a larger minimum approach distance at the scene of the
incident.
•
Always treat every item of electrical equipment and any overhead line as
live until the electricity supply industry representative confirms that it is free
from electrical hazards.
•
Always apply the MAD to any conductive item (for example, any vehicle) in
contact with electrical equipment not confirmed as being free from electrical
hazards.
7 Managing mechanical hazards
On arrival at an incident involving an electricity supply industry asset, it is
important to identify any potential mechanical hazards in addition to electrical
hazards (outlined in section 6).
Hazards that may be present include:
•
Electricity poles (or other equipment) that have been compromised due to
impact by a vehicle (see Figure 9); or
•
Cable failure under tension (see Figure 10).
•
Pole-mounted equipment that may fall (transformer, switchgear or
hardware).
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Figure 9: Electricity pole compromised by an incident
Figure 10: Cable failure under tension
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8 Responding where electrical hazards are present
8.1
Communicating with the electricity supply industry
It is very important that electricity supply industry organisations and emergency
services have in place pre-agreed communication plans to ensure that when an
incident occurs that actions taken to rescue injured persons can be done in an
efficient and co-ordinated manner where all parties understand each other’s
responsibilities (see Appendix C).
All electricity network companies have control rooms with good communications.
The control room operators run their electricity networks and are in charge of all
switching. They are the contact point for network company support in any
incident involving the electricity network.
Emergency services should follow their pre-agreed communication plan on
becoming aware of any incident involving the network. Prompt advice may
significantly lessen the time between the incident and arrival on-site of competent
network company electrical staff. Once on-site they can help control the electrical
hazards.
Various factors can influence the time it takes for an electricity supply industry
representative to reach the scene of an incident. Factors include whether the
incident has occurred in a rural or urban area (traffic can increase the time to
respond and ability to locate the incident in a rural area can increase response
time). If multiple incidents have occurred at the same time (e.g. during a storm
event) this can increase the time to respond.
A key factor in arriving to the site quickly is ensuring accurate information on the
location and details of an incident. The following information will help:
1.
Information that enables the ESI to precisely identify the scene:
‒
Location (street address or rapid number or GPS location/co-ordinates
or closest intersections)
‒
Asset number of power pole or nearby asset number (or ID)
‒
Landmarks.
2.
Type of asset (as per Appendix A).
3.
Nature of the failure (e.g. broken pole; wires down; car versus pole etc).
4.
Any life-threatening situation.
The electricity supply industry representative who arrives on-site to make it safe
from electrical hazards in order for the emergency services personnel to
undertake rescue must follow a strict set of steps. This is called the hierarchy of
control. The steps involve the following:
1.
Eliminating the risk.
2.
Minimising the risk (for example by isolating).
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The electricity supply industry representative who attends the incident contacts
the incident controller as they arrive on-site and would keep the incident
controller well informed about what steps were being taken to make the site safe
for emergency personnel to enter.
Direct phone numbers to electricity network control rooms are unlisted. This
prevents call swamping during emergencies. Unless directed otherwise,
emergency services and electricity network control rooms must follow
communications protocols based on pre-agreed communication plans
(suggested content of pre-agreed communication plans is included in Appendix
C).
Emergency services should ensure that their communications and protocols are
current and functioning according to the agreed plan.
8.2
Arriving on-site
On arrival at an incident involving electrical equipment, emergency services
personnel should follow the steps below:
22
•
Establish a cordon around the incident, where appropriate.
•
Everyone not directly involved with the rescue should keep well clear – at
least 8 m (see Figure 11);
•
Carry out a preliminary site hazard assessment (see 8.3);
•
Follow the pre-agreed communication plan with the electricity supply
industry organisation and identify the location of the incident (see 8.1);
•
Ask for on-site help. Follow the instructions received from the electricity
supply industry organisation. They will send a representative to the site.
•
Once on-site the electricity supply industry representative will identify the
incident controller and will make themselves known to the incident
controller. The electricity supply industry representative will provide regular
updates to the incident controller in situations where emergency services
response work is underway, to set clear expectations on how long it will
take and when extra equipment is required to make the site safe.
•
Electricity supply industry representatives are bound by Safety Manual –
Electricity Industry (SM-EI) rules. If the electricity supply industry
representative is requested to undertake a task by the incident controller
they will state whether it is possible or not and if not, why not.
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Figure 11: Keep the public at least 8 m from any fallen overhead lines
8.3
The site hazard assessment
Be cautious. Approaching the incident too closely before understanding the
hazards may expose personnel or others to serious electrical hazards. (See
Figure 12.)
Conduct the first hazard assessment from at least 8 m away, where possible, to:
•
Find out whether there is any contact with or damage to parts of the
electricity network in the immediate area;
•
Identify the parts of the network involved (see section 6 and Appendix A),
whether electrical equipment or overhead lines, transmission or distribution,
and gather key information;
NOTE: This includes, for example: region, district, street name, equipment
description, distinguishing features and any identification or tag number (if labelled),
any other information about the incident or status of the equipment.
•
Immediately advise the electricity network control room, providing as much
information as possible.
Requests for any electricity supply industry company to switch off any electricity
supply are weighed against potential adverse effects on customers and the
public. This is because electricity networks are critical to supporting essential
community services such as water, sewerage, hospitals, street lighting, traffic
lights and telecommunications. Removing electricity supply from any parts of
such networks potentially affects large numbers of people and may put the safety
of some at risk.
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Figure 12: Visually assess for electrical hazards before approaching
8.4
Approach distances
Treat all electrical equipment and all overhead lines as live until the electricity
supply industry representative confirms they are free from electrical hazards.
Where the equipment or lines are not yet confirmed free from electrical hazards,
emergency services personnel must maintain the MAD of 4 m.
8.5
Managing an incident site
The incident controller manages the incident site and the electricity supply
industry representative will identify themselves to the incident controller and keep
them updated on their actions to make the site safe from electrical hazards. The
incident controller is located within the cordon. Figure 13 illustrates this cordon
and the control of movements of persons at the scene of an incident.
Electricity supply industry representatives and emergency services personnel
can face pressure from the public to take shortcuts in making sites safe where
persons have been injured. This pressure should be managed by the incident
controller.
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Figure 13: Incident control point cordons
NOTE: For more details about specific terminology used in Figure 13 please refer to the New Zealand Coordinated Incident Management System (CIMS) 2014 edition.
9 Guidance for common incidents
In general, the guidelines in section 8 apply at all incidents involving electrical equipment and
overhead lines; however, further specific guidelines in this section cover the more common incidents.
A brief response procedure is given in Appendix D and Appendix E sets out core knowledge
components for emergency services personnel dealing with electrical hazards.
9.1
Victim at house building or factory involving live overhead lines
or electrical equipment
Where a person has come into contact with live overhead lines or electrical
equipment at a residential property (for example, with the service line to the
house) or factory take the following steps
•
Exercise extreme caution;
•
Apply the MAD;
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•
Only contact the victim or items involved in the electrical incident after the
electricity supply industry representative has confirmed the site is safe from
electrical or other hazards.
For typical houses and buildings where voltages are no more than 230/400 V –
on carrying out a dynamic risk assessment, if there is an immediate life risk,
isolate the electrical hazard by switching off the electrical supply at the
switchboard. If this is not achievable treat all wires as live until the electricity
supply industry representative has confirmed the site is safe from electrical
hazards. The electricity supply industry representative should attend in all cases.
Be aware that turning off the main switch will NOT isolate a service line.
NOTE: For victims within a house or factory follow specific procedures provided by
relevant emergency service.
9.2
Overhead line brought down by storm or fallen tree
Keep all members of the public at least 8 m from any fallen overhead line (and
anything in contact with the line) and advise the electricity network control room
immediately.
9.3
Vehicle into pole – overhead line down but not on vehicle
Emergency services personnel must maintain the MAD of 4 m from the overhead
lines, and the vehicle and any conductive items such as water pools.
•
If the driver is conscious and the vehicle is driveable, tell the driver to
remain in the vehicle and carefully drive to a safe distance from all the
electrical hazards before exiting the vehicle;
or
•
If the vehicle cannot move for any reason, leave the driver in the vehicle
and obtain confirmation that the overhead line is free from electrical hazards
before undertaking the rescue. Live overhead lines and conductive items in
the area not confirmed free from electrical hazards involve high step voltage
risks.
These incidents involve no direct or obvious contact between the vehicle and
overhead line. But check to ensure that no other hidden electrical contact exists,
such as crushed electric cables on poles, or crushed pillars or plinths under the
vehicle. If live, these involve high step and touch voltage risks at the site.
9.4
Vehicle into and contacting pole, overhead line or other
electrical equipment
Do not touch or indirectly contact any vehicle that is in contact with any groundmounted electrical equipment (see Figure 14), overhead line (see Figure 15), or
electric cable running up a pole. The vehicle body may be live, and vehicles in
contact pose significant step and touch hazards. Keep the MAD of 4 m and an
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equivalent distance from the vehicle and any conductive items, such as adjoining
wire fence or water pool.
Figures 16 and 17 illustrate other hazards such as pole or conductor collapse.
Figure 14: The whole vehicle can be live if it crushes a pillar – do not touch
Figure 15: A vehicle in contact with lines or equipment may be
live – keep at least 4 m away
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Figure 16: Following a crash, overhead lines can break and drape on the ground or on objects
nearby. Overhead lines may also pull tight with the possibility of breaking without warning
Check whether the vehicle is on top of or against any ground-mounted electrical
equipment since this may also liven the vehicle. (See Figure 18.)
Figure 17: Pole collapse on vehicle
Figure 18: Vehicle on ground-mounted
electrical equipment
Rubber tyres may insulate the vehicle from the ground but tyres can ignite and
burn. This increases risk of electric current travelling through the ground surface
in the immediate area.
If the driver is conscious and the vehicle is in working condition, tell the driver to
drive well clear of the overhead line, pole or electrical equipment. Ensure all
persons stay well clear; the moving vehicle may release lines and cause them to
spring up unexpectedly.
Contact the electricity network control room for help.
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Vehicle occupants will be safer if they stay in the vehicle; to leave the vehicle
while it is live or potentially live is dangerous at any voltage. Any person doing so
may create a path to earth for the electric current.
Other life-threatening risks such as fire might force an emergency evacuation
(self-rescue) from the vehicle even if it is live or potentially live. Evacuation can
be on to an insulated platform. Improvised platforms may, for example, be a layer
of several rubber car mats, layers of dry clothing (beware of metal attachments
such as zips and buttons), dry timber pallets, layers of plastic sheeting or other
insulating materials. The occupants should exit the vehicle by jumping onto the
insulated platform so there is no possibility of simultaneous contact with the
vehicle and the ground. (See Figure 19.)
If self-rescue is to be attempted then the following information should be
conveyed to the person attempting the self-rescue. Do not try this procedure for
voltages over 33 kV; this is too dangerous.
1.
If there is no imminent danger to the person attempting self-rescue they
should be strongly warned that they are safer staying where they are and
that the emergency services are preparing to come and get them shortly.
2.
If they try to move then they are in danger of electrocution or being badly
burnt.
3.
If self-rescue is to be attempted then the occupant needs to position
themselves so they can ensure they are steady and can jump as far as
possible from the car landing upright with two feet together on the ground
(see Figure 19.)
NOTE: Improvised insulated platforms have unknown electrical insulating properties,
especially in wet conditions. Use these only in extreme emergencies where occupants
face imminent life-threatening danger from other hazards. Otherwise, wait for an electricity
supply industry representative to arrive on-site to make the site safe from electrical
hazards.
Figure 19: A driver or passenger exiting the vehicle must jump well clear
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9.5
Machinery contacting overhead lines or underground cables
Transporting high loads such as buildings, cranes and raised tip truck trays
occasionally come into contact with overhead lines. Diggers and thrusting
machines can also contact overhead lines or, digging down, contact underground
cables. When this happens, the vehicle or machinery can become live. (See
Figures 20 and 21.)
•
Always check whether the vehicle or machinery is or may still be in contact
with the overhead line or underground cable. If so, the vehicle or machinery
is live or potentially live.
•
Apply the MAD of 4 m.
•
If the operator or driver is in the cab tell them to remain there until an
electricity supply industry representative arrives on-site and disconnects the
electricity supply.
The first choice should always be to make the site safe from electrical hazards
for safe access to the vehicle or machinery. For other life-threatening
emergencies or risks such as fire, an emergency rescue may be necessary. If so,
do this according to the guidance in 9.4.
Figure 20: Where possible, the driver and any passengers should stay in the
vehicle until the site is safe from electrical hazards
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Figure 21: Underground cables
9.6
Person on overhead line pole or tower
Emergency services personnel should not attempt immediate rescue of any
person injured on a pole or tower, even if the overhead line (or lines) are taken
out of service by the electrical supply industry company. Electrical hazards
continue from other live circuits on the same structure, and there are also
significant fall hazards. Wait for an ESI representative to arrive.
Tell any uninjured person who is on a pole or tower to remain where they are and
to keep still with arms close into their body. Wait for electricity supply industry
representatives to arrive and make safe for rescue, in order for emergency
services to undertake rescue.
9.7
Person in substation
All substations are hazardous environments. They allow movement only for
competent electrical or specially trained people. Movement in substations,
whether at ground level or aloft, cannot necessarily allow safe distances from live
electrical equipment, especially when people carry conductive objects. Risks of
harm for people aloft are usually significantly higher than at ground level;
substations include many uninsulated high voltage conductors.
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People not trained to be in substations cannot tell the dangerous parts of these
by looking. High voltages can be present in substation enclosures and there are
often multiple supply connections into these sites, any or all of which could be
live.
Security fencing surrounds outdoor substations, but determined intruders
occasionally climb or cut their way into such enclosures, and all equipment within
is potentially dangerous.
Emergency services personnel must not enter a substation or substation
enclosure unless they have consent from, and are directly supervised by, an
electricity supply industry representative.
Most substations do not have permanent staff. A few larger ones have
maintenance staff or an operator on-site. Emergency services priority should be
to advise the electrical supply industry control room and seek expert help on-site
as soon as possible. Once on-site, the electricity supply industry representative
arranges any electrical equipment disconnection for rescue. Meantime, tell
intruders or others within any substation or enclosure that they are at extreme
risk and to follow your instructions. Tell them to remain still and to lessen bodily
movement until help arrives.
9.8
Fire under or near an overhead line
Hoses trained on fire, including on hot gasses or dense smoke, near any
overhead line can create a conductive path for electric current to earth. (See 6.5
and Figure 22). Wherever practicable, ask the electricity supply industry
representative to make the site safe from electrical hazards before fighting the
fire.
When fighting a fire close to a live overhead line, take particular care to:
•
Stand well back from the overhead line so the water jet-reach is as long as
possible;
•
Keep water jets away from direct contact with the overhead line;
•
Ensure that any emergency services personnel and members of the public
stay well clear of any potential fall or splatter zone;
Be aware that:
32
•
Overhead lines may break and fall to the ground because of the heat from a
fire;
•
Timber poles, crossarms and any pole-mounted equipment may fall;
•
Pole-mounted equipment can shatter or rupture, expelling debris, including
large quantities of oil that may catch on fire;
•
Smoke can increase the risk of arcing.
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Requests for any electricity supply industry company to switch off any electricity
supply are weighed against potential adverse effects on customers and the
public. This is because electricity networks are critical to supporting essential
community services such as water, sewerage, hospitals, street lighting, traffic
lights and telecommunications. Removing electricity supply from any parts of
such networks potentially affects large numbers of people and may put the safety
of some at risk.
Figure 22: Electric current can arc through smoke and flames, as
well as travel through water jets
9.9
Fire in a substation
All substation fires are especially dangerous, and it is necessary to develop a fire
control plan with the electricity supply industry company, as the basis for any
substation access or fire response.
Substation fires often result from electrical equipment failure, involving internal
arcing, explosion and fire. Items of electrical equipment filled with oil sometimes
fuel intense fire and thick conductive smoke. Also, the equipment may have
exploded or be on fire, but may remain live. Other substation equipment nearby
is also likely to be live.
Besides the electrical hazards from contact with live equipment, fire hose use
involves hazards similar to those outlined in 9.8.
Other, by no means exclusive, hazards in substation fire include:
•
Damaged equipment near to a burning section exploding without warning,
expelling burning oil, toxic gas, broken porcelain and other debris;
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•
Large volumes of burning oil expelled;
•
Dense smoke may trigger arcing;
•
Some substations contain cylinders of compressed gas, which could
explode;
•
Water and debris in a flooded enclosure significantly increasing the extent
and severity of an electrically dangerous area.
Fires in enclosed (indoor) substations present particular hazards:
•
Electrical equipment in a confined enclosed area, and potential ventilation
or extraction failure from power disruption;
•
Trapped dense smoke, increasing arcing risk, and asphyxiation risk to
trapped people;
•
Extreme heat, thick smoke, explosion risk and electrical dangers create an
especially hazardous environment for trapped people and their rescuers.
9.10 Floods
Any water close to live electrical equipment can make normally safe areas
dangerous. Water conducts electric current and increases the risk of arcing.
During floods, parts of buildings and large tracts of land may be covered in water,
affecting electrical equipment located underground and at or near ground level.
Such equipment may include pillars, transformers and substations. Do not
approach or touch electrical equipment in floodwater; immersed equipment can
have dangerous voltages. Also, electricity network towers and poles could
become unstable and may cause overhead lines to sag or fall.
Boat use in flood conditions can involve navigation much closer to overhead lines
than normal. Cross under overhead lines only where there is plenty of clearance
between the highest point of the boat and the lines. Acceptable clearance
depends on the overhead line voltage: if unknown, cross under at a point of
maximum available clearance.
Bodily contact with any live wall or overhead fittings (e.g. broken light bulb or light
fitting) within a flooded building is a lethal combination. Such contact even while
only partly immersed effectively earths the body, involving potentially lethal
currents to earth. Never touch any electrical equipment or fitting in a flooded
building until it has been made safe from electrical hazards and clearance given
by the electricity supply industry representative.
9.11 Storms
Storm events often result in multiple incidents that present electrical and
mechanical hazards from the electricity network that can cause dangers to the
public. In these situations there is often a need for emergency services to
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prioritise their response to incidents, which may cause delays in fault teams
reaching the scene of incidents.
ESI representatives will respond as quickly as possible to events as prioritised by
their organisation. The basic principles for responding to an incident remain
unchanged for storm events and MADs should be followed until electricity supply
industry representatives have made the incident scene safe.
9.12 Other incidents
Section 9 does not address other less common incidents. Emergency service
responses to such incidents should always conform to the recommended
practices in this Guide. This includes contacting the electricity supply industry
company for advice and help before acting in any rescue or fire response that
involves electrical equipment, or overhead lines.
9.13 Additional considerations
Other electrical and mechanical hazards exist that are outside the responsibility
of the electricity supply industry; however emergency services personnel should
be aware of these hazards:
•
Electricity can be generated on-site at domestic and commercial/ industrial
sites. Examples are photovoltaic generation, fuel cells and so on;
•
Electric vehicles;
•
Trucks contacting overhead conductors can cause tyres and bearings on
vehicles to be compromised.
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Appendix A Identification of electricity supply industry
equipment
This Appendix illustrates examples of overhead lines and electrical equipment.
These help emergency services personnel to identify electricity network items to
support their communications with electricity supply industry representatives,
particularly their control rooms.
Figure A.1: Examples of distribution lines with various layers. These examples include: 33 kV
on the top crossarm, 11 kV on centre crossarm and 400V on bottom crossarm (left side); 11 kV
on the top crossarm and 400 V on the bottom crossarm (right side). Structures often carry
telecommunications including bundled fibre optic communications lines underneath the
overhead lines.
Figure A.2: Many electricity network poles carry some form of identification number. The
electricity supply industry company can usually tell the pole location from this.
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Figure A.3: Transpower 220 kV transmission lines
Figure A.4: Transpower transmission line signs provide identification information, for example
the line name (Oteranga Bay – Haywards A), tower number (1452), and voltage (500,000V)
Figure A.5: Transpower transmission substations are typically large and found near major
cities. Transpower substations have signs at the entry with the station name
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Figure A.6: Examples of outdoor zone substations
Figure A.7: Examples of enclosed building substations
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Figure A.8: Example of pole-mounted distribution substation (transformer)
Figure A.9: Examples of ground-mounted distribution substation (transformer)
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Figure A.10: Examples of connection points, often referred to as ‘pillars’ or ‘plinths’, between
the distribution network and the customer’s underground electricity supply
Figure A.11: Examples of switchgear, used to control the flow of electricity to specific areas of
the distribution network
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Figure A.12: An example of a high voltage underground electric cables
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Appendix B Electrical hazards – key points checklist
1.
Voltage and electric current are dangerous: Treat every overhead line and
item of electrical equipment as live until it is confirmed as safe. DO NOT
TOUCH.
2.
Search for identification on the pole, tower or electrical equipment, such as
the electricity supply industry company name, line name, pole number,
equipment ID number.
3.
Advise the electricity supply industry company control room:
‒
Describe the damaged overhead line or electrical equipment, complete
with any identifying information;
‒
Ask for electricity supply industry expert help.
4.
Identify everything that might be live, such as car bodies, metal fences,
metal roofing, pools of water, and trees with overhead lines touching them.
5.
Keep the public and anyone not directly involved in a rescue at least 8 m
from any live or potentially live items.
6.
Wait for the electricity supply industry representative to arrive and make the
overhead line or electrical equipment safe, before any rescue.
7.
For emergency services personnel conform to the MAD of 4 m.
8.
If a vehicle or machine is contacting a live overhead line or electrical
equipment, tell the occupants to stay in the vehicle and wait for the
electricity supply industry company to make the area safe and give
clearance that the scene has been made safe from electrical hazards.
9.
For voltages 33 kV or less: if the occupants have to exit because of other
dangers, they must jump clear, or exit onto an insulating platform such as
timber pallets, rubber mats, multiple layers of plastic sheeting, dry clothing.
Do not try this procedure for voltages over 33 kV; this is too dangerous.
Respect the MAD. Do not imperil yourself by trying direct rescue action for
occupants in a vehicle or machine that is live or that may be live.
10. Keep the number of people and the time spent close to the hazard area to
an absolute minimum. Withdraw to 8 m as soon as practicable.
11. Electricity network substations are dangerous. Follow the pre-agreed fire
control plan and only enter with help from an electricity supply industry
representative.
12. Never aim fire hoses directly at live electrical equipment or overhead lines,
especially bare lines. Water jets are conductive.
13. Fire, smoke and gasses may cause arcing to the ground so keep well clear.
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Appendix C Pre-agreed communication plans
Pre-agreed communication plans between the electricity supply industry
organisations and emergency services help all parties understand each other’s
responsibilities in responding to incidents. Such a communication plan would
include the following information:
1.
Unlisted direct numbers to both the electricity supply industry call centre and
the emergency services.
2.
Provision of incident location, its nature, asset identification information.
3.
Identification of responsible persons including incident coordinators.
4.
Provision of information detailing the status of response (i.e. estimated time
of arrival of fault persons).
5.
Provision of information on the status of work to make safe the incident site.
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Appendix D Brief response procedure
Potential electrical incident alarm raised, emergency services personnel sent
to site.
Electricity supply industry
company advised. Staff
dispatched.
On arrival at incident, keep
8 m away to conduct
hazard assessment.
Does someone need urgent
attention close to the
overhead line or electrical
equipment?
No
Stay 4 m away (keep public
8 m away). Wait for
Electricity supply industry
representative to arrive.
Yes
Can rescue be completed without being closer than 4 m from any items in
contact with the electricity source?
Yes
Proceed in
accordance with
approved
procedures.
44
No
Stay 4 m away. Wait for electricity
supply industry representative to
arrive.
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Appendix E Basic knowledge for emergency services
personnel on incidents involving electrical hazards
It is expected that emergency services personnel have a basic understanding of
the steps they should take when an electrical network hazard has been identified.
Personnel must be able to:
1.
Identify every potential electrical and mechanical hazards at the scene of an
incident involving an electrical network.
2.
Apply the Minimum Approach Distances (MADs).
3.
Identify the asset number on a piece of electrical equipment in order to
determine location.
4.
Understand that the electricity supply industry representative that responds
to an incident must follow the industry’s safety requirements in making the
site safe to effect rescue and that they will keep the incident controller
informed of their progress during an incident.
5.
Have the principles-based checklist ‘LIVE’ committed to memory.
(i)
Location of incident and assets involved
(ii) Identification of hazards from electricity network
(iii) View from at least 4 metres distance (and 8 metres for the public)
(iv) ESI clearance needed before approaching incident site
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Issued and published by the Electricity Engineers’
Association of New Zealand (Inc.) (EEA).
» First published May 1988
» Second edition published April 2009
Electricity Engineers’ Association (EEA)
Level 6, 138 The Terrace, PO Box 5324
Wellington, New Zealand
Phone
» Third edition published May 2015
Email
ISBN: 978-0-473-32447-6
Web
+64 4 473 8600
[email protected]
www.eea.co.nz
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