EN Hv cables with extruded corrugated aluminium screen

HIGH VOLTAGE CABLES WITH
EXTRUDED CORRUGATED
Aluminium SCREEN
Design
Available options
Advantages and disadvantages
Manufacturing process
TELE-FONIKA Kable S.A. PRODUCT BROCHURE
Over the last 20 years TELE-FONIKA Kable S.A. established itself as a global leader in the high voltage systems
market - supplying cable to more than 200 projects in over 40 counties around the world.
TELE-FONIKA Kable provide the highest quality and most durable cables, it’s advanced designs offer the most
efficient solution as part of the overall cable system.
This can only be achieved through a continual process of innovation and development. By combining our
knowledge in the field with detailed analysis of current market requirements, we are always one step ahead
by investing in the latest manufacturing technology.
It is through this process of innovation that TELE-FONIKA Kable identified a need in the marketplace for a
modern alternative to lead sheathed high voltage cables. The use of lead as a screening material has a long
history in many countries, but it is a heavy material which adds to installation complexities and it’s toxicity
has environmental issues.
The aluminium sheathed cables currently marketed as an alternative to lead use the ‘Fold and Weld’ process,
this includes a longitudinal welded join throughout the cable length. Concerns have been raised about
the integrity of this weld as no IEC or British Standard protocols exist to prove the strength of the join.
TELE-FONIKA Kable realized there was need in the High Voltage market for a more robust alternative to lead.
TELE-FONIKA Kable response to this challenge is the launch of an Extruded Corrugated Aluminium Sheathed
high voltage cable utilising SheathEx™ technology. Extruded aluminium sheathed medium voltage utility
cables has a proven history of reliability in the UK since the 1970’s, TELE-FONIKA Kable have enhanced this
process for high voltage cables.
TELE-FONIKA Kable investing in the manufacturing methods of the present and now the energy efficient
SheathEx™ Extruded Corrugated Aluminium Sheathing technology of the future!
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Extruded Aluminium Sheaths - model
CONDUCTOR
High purity compacted stranded copper or aluminium.
Extruded semi-conducting conductor screen
Ensures a uniformly stressed interface with the insulation.
INSULATION XLPE
Nitrogen dry cured XLPE dielectric.
EXTRUDED SEMI-CONDUCTING INSULATION SCREEN
Ensures a uniformly stressed interface with the insulation.
SEMI-CONDUCTING SWELLING TAPES
Provides a water barrier to prevent the longitudinal propagation
of water.
METALLIC CORRUGATED SHEATH: EXTRUDED Aluminium
Prevents the radial ingress of moisture.
Corrugated sheath profile in combination with the water swellable
tapes prevents longitudinal propagation of water.
Protect cable core against mechanical damage.
Conducts capacitive charging current to ground in normal
operation and short circuit currents in the event of a fault.
BITUMINOUS TAPES
Provides additional corrosion protection of the aluminium layer
in the event of localised mechanical damage.
OUTER SHEATH
Provides protection of the metallic screen. There are options for
the composition of the sheath depending on the intended use
includes resistance against fire, oils, termites, and rodents.
Also a semiconductive layer can be applied to the outer sheath if
required; this can be extruded coating or graphite depending on
preference.
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WHAT CABLE SCREEN OPTIONS ARE AVAILABLE
There are various terms used to describe the metallic barrier on a high voltage cable: ‘Metallic Sheath’, ‘Cable
Screen’, ‘Return Conductor’. These terms all describe the metallic layer that concentrically surrounds the
cable core.
There are the following types of cable screens:
Extruded aluminium
Longitudinally welded aluminium
Extruded lead
Laminated foil screen with copper wires bonded to the cable sheath.
The above-types of screens are accepted by the main international standards IEC 60840, HD 632 or
British BS 7912.
ADVANTAGES AND DISADVANTAGES OF DIFFERENT CABLE SCREENS
Advantages
Disadvantages
Larger Cable Diameter
TFK Corrugated Extruded
aluminium
Low cost
Proven usage history
Good conductivity
Low weight
Longer pulling in lengths
Lower shipping costs
Good environmental properties
High crush resistance
Continuous extrusion- so no weld or overlaps
Long lengths
Aluminium Foil + Copper wire
Good conductivity in copper wires
Good environmental properties
Possibility of manufacturing long lengths
Proven usage history in Europe
Adhesive foil seal can fail
Low usage in some countries
Short circuit carried by copper wires rather than foil
covering
Good corrosion resistance
Long service history
Continuous extrusion- so no weld or overlaps
Very Heavy Material
Poor conductivity
Bad material for environmental concerns
High production costs
Can crystallize and crack over time
Low cost
No requirement for hot tooling
Lightweight material
No established tests to certify the reliability of weld
Weld bead formed on sheath
Large bending radius.
Increased shipping and installation costs.
If welded corrugated-design - the corrugations are
added after the weld increasing strain on weld bead.
Limited sheath thickness
Lead screen
Welded aluminium
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Extruded Aluminium Sheaths – Manufacturing Processes
Hydraulic Press
In the past, the method of producing extruded aluminium
screens was by a hydraulic press. Aluminium ingots were
fed into the press, preheated, then huge pressure exerted to
extrude flowing aluminium onto the cable.
This was a very expensive process and consumed vast amounts
of energy.
There were limitations on cable lengths using this process, also
risk of heat damage when process stops to refill with aluminium
ingots.
Conform Process
The Conform™ process is a far more efficient method of
extruding aluminium sheaths onto cable.
This process relies on a combination of frictional heat generated
by the rotating wheel and a heated die chamber.
Revolving wheel takes aluminium rod into the peripheral
grooves.
Aluminium rod is fed into the die chamber by way of peripheral
grooves. There is an abutment in the grooves that forces the
aluminium to flow plastically into the heated die chamber. The
plastic state metal flows into the die chamber and out through
an over sized die.
The Extruded tube of aluminium is rapidly cooled immediately
after the die to prevent heat damage to the cable.
Extruded aluminium tube is corrugated inline as part of the
continuous process.
* Conform and SheathEx graphics reproduced by permission of BWE Ltd.
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Comparison of physical and electrical properties of 1000 mm2 copper
conductor 76/132 kV cable with an extruded corrugated aluminium sheath,
an aluminium foil with copper wire and a lead sheath with copper wire.
Properties
Description
Cable design
[mm]
Type of cable metallic screen
Cu wires +AL. foil
Cu wires + Extruded Pb
Extruded corrugated AL
2XS(FL)2Y
2XS(F)K2Y
2X(F)KLD2Y
Conductor diameter (mm)
38.2
Insulation thickness (mm)
15.0
Diameter over insulation (mm)
70.8
Quantity x diameter of Cu wire
(mm)
90 x 2.20
72 x 2.2
-
Lead layer thickness Pb (mm)
-
3.0
-
Aluminium layer thickness Al.
(mm)
-
-
2
335 + 54Al
270Cu + 750Pb
520
Cross-section of metallic screen
(mm2)
Outhersheath thickness (mm)
3.8
4.0
4.2
Diameter (mm)
87.5
94.0
99.6
Cable weight kg/m
16.40
24.80
15.90
Bending radius
Example packing
lengths/drum flange
Cable screen
properties
Current Rating
[A]
0.050
0.055
0.053
Weight of metalic screen kg/m
3.31
2.80Cu + 9.13Pb
1.87
Bonding type
Underground – flat
Sheath losses
Induced voltage
Sheath current
Underground - trefoil
Total losses
[W/m]
Screen losses λ1
Sheath losses
1216/754
1159/753
0/2.200
0/2.3600
0/2.3600
0/33.27
0/34.93
0/23.21
38.83/48.36
39.71/49.74
39.90/38.17
113.6/---
117.1/---
146.0/---
---/667
---/467
---/620
1083/830
1085/829
999/822
0/0.900
0/0.963
0/0.9850
0/17.05
0/18.02
0/18.00
33.88/36.73
34.25/36.49
Induced voltage
54.9/---
57.1/---
54.8/---
Sheath current
---/536
---/513
---/516
Air - flat
Sheath current
[A]
Single point bonding / Both end bonding
1210/760
33.21/36.00
Total losses - per phase
Induced voltage
[V/km]
650m/34
850m/37
1100m/40
40.0kA/3s
Screen short ciruit kA/s
Total losses – per phase
Sheath losses
[W/m]
400m/34
Screen resistance Ω/km
Screen losses λ1
Screen losses λ1
25 x De
900m/34
1200m/37
1500m/40
1656/1176
1675/1181
1568/1155
Screen losses λ1
0/2.1700
0/2.3200
0/2.3100
Sheath losses
0/78.38
0/84.45
0/53.84
Total losses - per phase
72.88/114.5
75.38/120.8
72.58/115.27
Induced voltage
155.6/---
161.2/---
196.9/---
Sheath current
---/1030
---/731
---/958
Air - trefoil
1423/1166
1443/1182
1333/1158
Screen losses λ1
0/0.9040
0/0.9680
0/0.9900
Sheath losses
0/33.79
0/36.84
0/35.91
57.35/71.17
59.97/74.90
61.00/72.38
Induced voltage
Total losses - per phase
71.8/---
76.1/---
72.7/---
Sheath current
---/760
---/732
---/738
Calculated with CymCap 5.3 based on IEC Pub. 60287 and the following conditions: Ground temperature 20°C, Ground thermal resistivity 1.0
K*m/W, Laying depth 1.2m, Air temperature 35°C
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WHY CHOOSE AN EXTRUDED CORRUGATED Aluminium SCREENED
CABLE?
LIGHTWEIGHT – HV cables with extruded corrugated aluminium screens are less weight compared to
other types of metal screens, this reduces transportation costs and makes the cable easier to install.
ELECTRICAL PERFORMANCE - extruded corrugated aluminium screen is characterised by high electrical
conductivity capable of carrying higher short circuit currents.
NO NEED FOR COPPER WIRES – due to the superior electrical performance of extruded corrugated
aluminium screens it is not necessary to add copper wires under the screen to carry high fault current
requirements. Even the highest UK short circuit requirement of 40 kA for 3 seconds can be easily
carried by an aluminium screen of 2 mm thickness. (see table above)
BENDING RADIUS - The corrugations in the extruded aluminum sheath offer a tighter bending (typically
25 x cable diameter) compared to smooth welded aluminium cable (35 x cable diameter).
DURABILITY - Aluminium has excellent mechanical properties including hardness and fatigue resistance
compared to lead sheath cables. Aluminium offers superior resistance to vibration and movement
caused by mechanical thrust and thermal cycles encountered during current loading transients.
LESS ENVIRONMENTAL IMPACT – Aluminium is a clean metal, both in the manufacturing process and
for continued installation, whereas lead is considered a hazardous substance by the EU’s RoHS directive
20002/95/EC.
PROVEN RELIABILITY – Extruded aluminium sheathed medium voltage cables were produced in the UK
from the 1970’s until the early 21st Century. Promoted as the latest sheathing solution, thousands of
kilometers are still in continuous service, proving the long term reliability of the design.
LATEST TECHNOLOGY - The closure of many UK manufacturers meant extruded aluminium sheathed
cables disappeared from the market… until now!
TFK are offering the same proven reliability but with an improved and more efficient method of
production.
ACCEPT NO IMITATIONS!
Some manufacturers are offering an aluminium sheathed cable that have been corrugated after welding.
This is not the same product. TELE-FONIKA Kable S.A. offer a SEAMLESS aluminium sheath where the
corrugations are formed as part of the extrusion process whilst the aluminium is in a molten state.
A STRESS FREE DESIGN FOR A STRESS FREE INSTALLATION!
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TELE-FONIKA Kable S.A.
HEADQUARTERS:
Wielicka 114, 30-663 Krakow, Poland
Tel.: +48 (12) 652 5000, Fax: +48 (12) 652 5156
HIGH VOLTAGE TEAM:
Tel.: +48 (12) 372 7301, +48 (12) 372 7302, +48 (12) 372 7303, +48 (12) 372 7304
All the information contained in this document - including tables and diagrams - is given in good faith and believed to be correct at
the time of publication. The information does not constitute a warranty nor representation for which TELE-FONIKA Kable assumes
legal responsibility. TELE-FONIKA Kable reserves rights to introduce changes to the document at any time.
Edition II