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Medium Voltage Cables |  |
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| Medium Voltage Cables to BS 6622 |  |
Medium Voltage Cables to IEC 60502 | |
Medium Voltage Cables to VDE 0276 |
Medium Voltage Cables to BS 6622
Three Core Cables to BS 6622
Application
The three core cables are designed for distribution of electrical power with nominal voltage Uo/U ranging from
3.6/6.6KV to 19/33KV and frequency 50Hz. They are suitable for installation mostly in power supply stations,
indoors and in cable ducts, outdoors, underground and in water as well as for installation on cable trays for
industries, switchboards and power stations.
Standards
BS 6622
Construction
Conductor: Plain annealed copper or aluminium complying with IEC 60228/BS 6360. Copper conductors shall be
stranded (class 2) and aluminium conductors shall be either solid or stranded (class 2).
Conductor Screen: Extruded layer of semi-conducting cross-linkable compound is applied over the conductor
and shall cover the surface completely. The minimum thickness is 0.3mm and the maximum resistivity shall not
exceed 500 Ohm-m at 90°C.
Insulation: Insulation is of cross-linked polyethylene compound XLPE (GP8) conforming to BS 7655-1.3 or EPR
(GP7), conforming to BS 7655-1.2.
Table 1. Insulation Thickness
| Nom. Cross Section Area |
Insulation Thickness at Nom. Voltage | ||||
|---|---|---|---|---|---|
| 3.8/6.6KV (Um=7.2KV) |
6.35/11KV(Um=12KV) | 8.7/15KV(Um=17.5KV) | 12.7/22KV(Um=24KV) | 19/33KV(Um=36KV) | |
| mm² | mm | mm | mm | mm | mm |
| 70 – 185 | 2.5 | 3.4 | 4.5 | 5.5 | 8.0 |
| 240 | 2.6 | 3.4 | 4.5 | 5.5 | 8.0 |
| 300 | 2.8 | 3.4 | 4.5 | 5.5 | 8.0 |
| 400 | 3.0 | 3.4 | 4.5 | 5.5 | 8.0 |
| Above 500 | 3.2 | 3.4 | 4.5 | 5.5 | 8.0 |
Insulaton Screen:
Extruded layer of semi-conducting cross-linkable compound is applied over the insulation. The extruded semi-
conducting layer shall consist of bonded or cold strippable semi-conducting compound capable of removal for
jointing or terminating. As an option, a semi -conducting tape may be applied over the extruded semi-conducting
layer as a bedding for the metallic layer. The minimum thickness is 0.3 mm and the maximum resistivity is 500
Ohm-m at 90°C. The screen is tightly fitted to the insulation to exclude all air voids and can be easily hand
stripped on site.
Inner Covering & Fillers:
For cables with a collective metallic layer or cables with a metallic layer over each individual cores with additional
collective metallic layers, semi-conducting inner covering and fillers shall be applied over the laid up cores. The
inner covering is made of non hygroscopic material, except if the cable is to be made longitudinally watertight.
The inner covering shall be extruded or lapped.
The approximate thickness of extruded inner coverings is given in Table 2:
Table 2. Approximate Thickness Of Extruded Inner Coverings
| Ficititous Diameter Over Laid Up Cores | Approx. Thickress of Extruded Inner Covering | |
|---|---|---|
| mm | mm | |
| > | < | |
| - | 25 | 1.0 |
| 25 | 35 | 1.2 |
| 35 | 45 | 1.4 |
| 45 | 60 | 1.6 |
| 60 | 80 | 1.8 |
| 80 | - | 2.0 |
*The approximate thickness of lapped inner coverings shall be 0.6mm.
Metallic Layer
The metallic layer shall be applied over each core or applied as a collective screen. The metallic screen shall
consist of either copper tapes or a concentric layer of copper wires or a combination of tapes and wires. The
metallic layer provides an earth fault current path, capable of withstanding fault current to earth of 1000A for
one second at maximum temperature 160°C. Copper wires are applied over the conducting water blocking layer
with a minimum diameter of 0.5mm. As an alternative, copper tape(s) with minimum thickness of 0.1mm can be
applied with overlap. Total cross section of copper wire screen and copper tape screen layer are shown in Table
3a and 3b.
Table 3a. Total Cross Section and Max. DC Resistance of Copper Wire Screen
Nominal Cross- |
Total Cross Section |
Max. DC Resistance of Copper Wire |
||||
|---|---|---|---|---|---|---|
3.8/6.6KV (Um=7.2KV) |
6.35/11KV (Um=12KV) |
8.7/15KV (Um=17.5KV) |
12.7/22KV (Um=24KV) |
19/33KV (Um=36KV) |
||
mm² |
mm² |
Ω |
||||
70 |
16 |
16 |
16 |
16 |
16 |
1.19 |
95 |
16 |
16 |
16 |
16 |
16 |
1.19 |
120 |
16 |
16 |
16 |
16 |
16 |
1.19 |
150 |
25 |
25 |
25 |
25 |
25 |
0.759 |
185 |
25 |
25 |
25 |
25 |
25 |
0.759 |
240 |
25 |
25 |
25 |
25 |
25 |
0.759 |
300 |
25 |
25 |
25 |
25 |
25 |
0.759 |
400 |
35 |
35 |
35 |
35 |
35 |
0.271 |
500 |
35 |
35 |
35 |
35 |
35 |
0.271 |
630 |
35 |
35 |
35 |
35 |
35 |
0.271 |
Table 3b. Total Cross Section and Max. DC Resistance of Copper Tape Screen (0.1mm)
Nominal Cross- Section of Cables |
Total Cross Section & Max DC Resistance |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
3.8/6.6KV (Um=7.2KV) |
6.35/11KV (Um=12KV) |
8.7/15KV (Um=17.5KV) |
12.7/22KV (Um=24KV) |
19/33KV (Um=36KV) |
||||||
Total |
Max. DC |
Total |
Max. DC |
Total |
Max. DC |
Total Cross Section |
Max. DC |
Total |
Max. DC |
|
mm² |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
70 |
6.6 |
2.616 |
7.23 |
2.380 |
8.02 |
2.145 |
8.7 |
1.967 |
10.5 |
1.075 |
95 |
7.3 |
2.369 |
7.91 |
2.174 |
8.71 |
1.975 |
9.4 |
1.824 |
11.2 |
1.075 |
120 |
8.0 |
2.153 |
8.64 |
1.991 |
9.43 |
1.823 |
10.2 |
1.694 |
12.0 |
1.075 |
150 |
8.5 |
2.013 |
9.19 |
1.871 |
9.99 |
1.722 |
10.7 |
1.606 |
12.5 |
0.688 |
185 |
9.4 |
1.838 |
9.88 |
1.741 |
10.82 |
1.590 |
11.4 |
1.509 |
13.2 |
0.688 |
240 |
10.4 |
1.656 |
10.96 |
1.569 |
11.76 |
1.463 |
12.5 |
1.378 |
14.3 |
0.688 |
300 |
11.4 |
1.508 |
11.84 |
1.452 |
12.64 |
1.361 |
13.4 |
1.287 |
15.2 |
0.688 |
400 |
12.6 |
1.362 |
12.92 |
1.332 |
13.71 |
1.254 |
14.4 |
1.192 |
16.2 |
0.491 |
500 |
13.9 |
1.237 |
14.34 |
1.199 |
15.14 |
1.136 |
15.5 |
1.110 |
17.7 |
0.491 |
630 |
15.3 |
1.121 |
16.68 |
1.031 |
16.57 |
1.038 |
17.3 |
0.995 |
19.1 |
0.491 |
Separation Sheath (for armoured cable):
The separation sheath comprises a layer of extruded PVC, PE or LSZH. The nominal thickness is calculated by
0.02Du + 0.6mm where Du is the fictitious diameter under the sheath in mm. The nominal separation sheath
thickness shall not be less than 1.2mm.
Armour (for armoured cable):
The armour consists of galvanized steel wire applied over the inner covering with diameter specified as in Table
4.
Table 4. Armour Wire Diameter
| Fictitiious Diameter Under the Armour | Armour Wire Diameter | |
|---|---|---|
| mm | mm | |
| > | < | |
| 25 | 1.6 | |
| 25 | 35 | 2.0 |
| 35 | 60 | 2.5 |
| 60 | - | 3.15 |
Over Sheath:
Overall sheath comprises a layer of extruded either PVC type 9 conforming to BS 7665-4.2 or MDPE type TS2
conforming to BS 7655-10.1; LSZH can be offered as an option. The oversheath is normally black in colour. When
a DC voltage test is to be performed on the oversheath, a semi-conducting layer such as graphite coating shall
be applied over the surface of the extruded oversheath. The nominal oversheath thickness is calculated by
0.035D+1 where D is the diameter immediately under the oversheath in mm. For cables with the oversheath not
applied over the armour, the nominal oversheath thickness shall not be less than 1.4mm. And for cables with
oversheath applied over the armour, the nominal oversheath thickness shall not be less than 1.8mm.
PHYSICAL PROPERTIES:
Operating Temperature: up to 90°C
Temperature Range: -5°C ( PVC sheath ); -20°C ( PE sheath )
Short Circuit Temperature: 250°C (short circuit duration up to 5 seconds)
Bending Radius: 12 x OD
Table 5. Nominal /Operating /Test Voltages
| Rated Voltage Uo/U | Operating Voltage (Um) | Testing Voltage (rms) |
|---|---|---|
| 3.8/6.6KV | 7.2KV | 15KV |
| 6.35/11KV | 12KV | 25.5KV |
| 8.7/15KV | 17.5KV | 35KV |
| 12.7/22KV | 24KV | 51KV |
| 19/33KV | 36KV | 76KV |
Three Core 3.8/6.6KV (Um=7.2KV) Dimensional Data
Nom. |
Nom. Insulation Thickness |
Copper Wire Screen Area |
Copper Tape Screen Area |
Nom.Bedding Thickness |
Nom. Armour Wire Diameter |
Nom.Sheath Thickness |
Approx. Overall Diameter |
Approx. Weight |
|
|---|---|---|---|---|---|---|---|---|---|
CU |
AL |
||||||||
mm² |
mm |
mm² |
mm² |
mm |
mm |
mm |
mm |
kg/km |
|
70 |
2.5 |
16 |
6.6 |
1.3 |
2.5 |
2.6 |
55.0 |
6570 |
5240 |
95 |
2.5 |
16 |
7.3 |
1.4 |
2.5 |
2.7 |
58.9 |
7760 |
5890 |
120 |
2.5 |
16 |
8.0 |
1.5 |
2.5 |
2.8 |
62.1 |
8810 |
6510 |
150 |
2.5 |
25 |
8.5 |
1.5 |
2.5 |
2.9 |
65.8 |
10110 |
7310 |
185 |
2.5 |
25 |
9.4 |
1.6 |
2.5 |
3.0 |
69.5 |
11520 |
7960 |
240 |
2.6 |
25 |
10.4 |
1.7 |
2.5 |
3.2 |
75.9 |
13920 |
9140 |
300 |
2.8 |
25 |
11.4 |
1.8 |
3.15 |
3.5 |
83.1 |
17400 |
11620 |
400 |
3.0 |
35 |
12.6 |
2.0 |
3.15 |
3.7 |
93.0 |
21900 |
13980 |
Electrical Data
Nom. Cross- Section Area |
D C |
A C |
Short Circuit Rating of Conductor CU / AL |
Capaci- tance |
Charging Current |
Short Circuit Rating of Screen 1 sec |
|
Current Ratings |
|||||||
Reac- tance |
Induc- tance |
Ground |
Duct |
Air |
|||||||||||
Copper Wire |
Copper Tape |
CU |
AL |
CU |
AL |
CU |
AL |
||||||||
mm² |
µΩ/m |
µΩ/m |
kA |
pF/m |
mA/m |
kA |
µΩ/m |
nH/m |
A |
A |
A |
||||
70 |
268/443 |
343/568 |
9.8/6.3 |
383 |
0.46 |
1.96 |
0.96 |
97 |
310 |
255 |
195 |
215 |
165 |
270 |
210 |
95 |
193/320 |
248/410 |
13.3/8.5 |
432 |
0.52 |
1.96 |
1.06 |
92 |
290 |
300 |
230 |
255 |
200 |
330 |
250 |
120 |
153/253 |
196/325 |
17.2/11.0 |
474 |
0.57 |
1.96 |
1.17 |
89 |
280 |
340 |
265 |
290 |
225 |
375 |
295 |
150 |
124/206 |
159/265 |
21.2/13.5 |
511 |
0.61 |
3.06 |
1.25 |
87 |
280 |
380 |
295 |
330 |
255 |
430 |
330 |
185 |
99/164 |
128/211 |
26.6/17.0 |
562 |
0.67 |
3.06 |
1.37 |
86 |
270 |
430 |
335 |
370 |
290 |
490 |
385 |
240 |
75/125 |
98/161 |
34.9/22.3 |
602 |
0.72 |
3.06 |
1.52 |
83 |
260 |
490 |
380 |
425 |
335 |
570 |
450 |
300 |
60/100 |
80/130 |
43.8/28.0 |
622 |
0.75 |
3.06 |
1.67 |
82 |
260 |
540 |
435 |
470 |
375 |
650 |
510 |
400 |
47/78 |
64/102 |
57.3/36.6 |
648 |
0.78 |
4.29 |
1.84 |
80 |
250 |
590 |
480 |
520 |
420 |
700 |
570 |
Three Core 6.35/11KV (Um=12KV)
Three Core 8.7/15KV (Um=17.5KV)
Three Core 12.7/22KV (Um=24KV)
Three Core 19/33KV (Um=36KV)