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XLPE
INSULATED POWER CABLES
CABLE TYPE (Al-)XLPE/SWA
flat/PVC 6-35 kV
DESCRIPTION Three-core
XLPE/SWAF/PVC cable is being made in accordance with IEC
60502/98. Copper or aluminium compacted stranded circular conductor,
conductor screen of extruded layer of semi-conducting XLPE, XLPE
insulation, insulation screen of extruded layer of semi conducting XLPE,
semi-conducting bedding tape, metallic screen consisting of copper wires
applied helically with a counterspiral of copper tape. Three cores are
being laid-up together with suitable fillers, covered with PVC separation
sheath, armoured with flat galvanized steel wires and covered with PVC
outersheath over in black colour.
Minimum bending
radius:
|
cable during instalation |
cable placed in position
adjacent to joints or terminations |
NON-ARMOURED |
15D |
12D |
ARMOURED |
12D |
10D |
D - outer cable
diameter
Current carrying capacity has been calculated according to IEC
287/82 (100 % load factor) and following conditions:
- Depth of laying 0.70 m, and for 20/35 kV
cables 1.0 m.
- Soil thermal resistivity 1.0 K
m/W.
- Ground temperature 20oC,
ambient air temperature 30oC, maximum conductor operating
temperature 90oC.
Type of laying :
- Sheaths bonded at both ends of an
electrical section
RATING FACTORS
|
Ambient temperature
oC |
15 |
20 |
25 |
30 |
35 |
40 |
Factor |
Cable in
ground |
1.04 |
1.00 |
0.96 |
0.93 |
0.89 |
0.85 |
Cable in air |
1.14 |
1.09 |
1.05 |
1.00 |
0.95 |
0.90 |
|
Soil thermal resistivity
(Km/W) |
Factor |
0.7 |
1.0 |
1.2 |
1.5 |
2.0 |
2.5 |
3.0 |
1.12 |
1.00 |
0.94 |
0.86 |
0.77 |
0.71 |
0.66 |
COMPARISON OF CHARACTERISTIC VALUES OF
INSULATING COMPAUNDS
|
Type of insulating
compaunds |
UPET |
PET |
PVC |
Maximum continous conductor operating temperature
oC |
90 |
70 |
65 |
Maximum conductor short-circuit temperature
oC |
250 |
150 |
160 |
Dielectric power factor at 50Hz,
20oC |
4 x
10-4 |
2 x 10
-4 |
10-2 |
Relative permittivity at 50Hz,
20oC |
2.3 |
2.3 |
4-8 |
Volume resistivity at 20oC
ohm.cm |
1017 |
1017 |
1014 |
Thermal resistivity K.m/W |
3.5 |
3.5 |
6.0 |
Tensile strenth, minimum
N/cm2 |
200 |
150 |
250 |
Elongation-at-break, minimum % |
350 |
550 |
250 | |
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