Medium Voltage Cables | |||
Medium Voltage Cables to BS 6622 | Medium Voltage Cables to IEC 60502 | Medium Voltage Cables to VDE 0276 |
Medium Voltage Cables to BS 6622
Single Core Cables to BS 6622
Application
The single core cables are designed for distribution of electrical power with nominal voltage Uo/U ranging from
3.8/6.6KV 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
BS 7835 (LSZH)
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 Nominal 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.
Metallic Layer
The metallic layer 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 2a and 2b.
Table 2a. Total Cross Section and Max. DC Resistance of the screen
Table 2a. Total Cross Section and Max. DC Resistance of Copper Wire Screen
Nominal Cross- |
Total Cross Section |
Max. DC Resistance of Copper Wire Screen at 20℃ |
||||
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 |
0.217 |
630 |
35 |
35 |
35 |
35 |
35 |
0.271 |
Table 2b. Total Cross Section and Max. DC Resistance of Copper Tape Screen (0.1mm)
Nominal Cross- Section of |
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 Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance at |
|
mm² |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
70 |
7.4 |
2.314 |
8.2 |
2.106 |
9.1 |
1.897 |
9.9 |
1.740 |
11.9 |
1.442 |
95 |
8.2 |
2.095 |
8.9 |
1.923 |
9.8 |
1.748 |
10.7 |
1.614 |
12.7 |
1.354 |
120 |
9.0 |
1.905 |
9.8 |
1.761 |
10.7 |
1.613 |
11.5 |
1.498 |
13.5 |
1.272 |
150 |
9.7 |
1.781 |
10.4 |
1.655 |
11.3 |
1.523 |
12.1 |
1.420 |
14.2 |
1.215 |
185 |
10.6 |
1.626 |
11.2 |
1.540 |
12.2 |
1.407 |
12.9 |
1.335 |
14.9 |
1.153 |
240 |
11.7 |
1.465 |
12.4 |
1.388 |
13.3 |
1.294 |
14.1 |
1.219 |
16.2 |
1.065 |
300 |
12.9 |
1.334 |
13.4 |
1.285 |
14.3 |
1.204 |
15.1 |
1.139 |
17.1 |
1.003 |
Nominal Cross- Section of |
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 Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance |
Total Cross Section |
Max. DC Resistance at |
|
mm² |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
mm² |
Ω |
400 |
14.3 |
1.205 |
14.6 |
1.178 |
15.5 |
1.110 |
16.3 |
1.054 |
18.4 |
0.937 |
500 |
15.7 |
1.094 |
16.2 |
1.061 |
17.1 |
1.005 |
17.5 |
0.982 |
20.0 |
0.861 |
630 |
17.3 |
0.992 |
18.9 |
0.912 |
18.7 |
0.918 |
19.5 |
0.880 |
21.6 |
0.797 |
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 round aluminium wire with diameter specified as in Table 3.
Table 3. Armour Wire Diameter
Fictitious 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+1.0 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: 15 x OD
Table 4. 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 |
Single 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 |
7.4 |
1.2 |
1.6 |
1.8 |
30.0 |
1740 |
1300 |
95 |
2.5 |
16 |
8.2 |
1.2 |
1.6 |
1.9 |
31.8 |
2030 |
1430 |
120 |
2.5 |
16 |
9.0 |
1.2 |
1.6 |
1.9 |
33.2 |
2310 |
1550 |
150 |
2.5 |
25 |
9.7 |
1.2 |
1.6 |
2.0 |
35.1 |
2660 |
1720 |
185 |
2.5 |
25 |
10.6 |
1.2 |
2.0 |
2.0 |
37.4 |
3120 |
1950 |
240 |
2.6 |
25 |
11.7 |
1.2 |
2.0 |
2.1 |
40.3 |
3740 |
2200 |
300 |
2.8 |
25 |
12.9 |
1.2 |
2.0 |
2.2 |
42.9 |
4400 |
2520 |
400 |
3.0 |
35 |
14.3 |
1.2 |
2.0 |
2.3 |
47.2 |
5490 |
2960 |
500 |
3.2 |
35 |
15.7 |
1.3 |
2.5 |
2.5 |
51.6 |
6760 |
3660 |
630 |
3.2 |
35 |
17.3 |
1.4 |
2.5 |
2.6 |
57.0 |
8200 |
4160 |
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 |
Reactance |
Inductance |
Impedance |
|||||||
Trefoil |
Flat spaced |
Trefoil |
Flat Spaced |
Trefoil |
Flat Spaced |
|||||||||||
Copper Wire |
Copper Tape |
|||||||||||||||
CU |
AL |
CU |
AL |
|||||||||||||
mm² |
µΩ/m |
µΩ/m |
kA |
pF/m |
mA/m |
kA |
µΩ/m |
µΩ/m |
nH/m |
nH/m |
µΩ/ m |
µΩ/m |
||||
70 |
268/443 |
343/568 |
9.8/6.3 |
371 |
0.45 |
1.96 |
1.09 |
115 |
173 |
370 |
550 |
364 |
583 |
386 |
597 |
|
95 |
193/320 |
248/410 |
13.3/8.5 |
417 |
0.50 |
1.96 |
1.20 |
110 |
168 |
350 |
540 |
272 |
427 |
300 |
446 |
|
120 |
153/253 |
196/325 |
17.2/11.0 |
459 |
0.55 |
1.96 |
1.32 |
107 |
165 |
340 |
520 |
225 |
345 |
257 |
367 |
|
150 |
124/206 |
159/265 |
21.2/13.5 |
494 |
0.59 |
3.06 |
1.41 |
103 |
161 |
330 |
510 |
193 |
287 |
229 |
313 |
|
185 |
99/164 |
128/211 |
26.6/17.0 |
543 |
0.65 |
3.06 |
1.54 |
100 |
158 |
320 |
500 |
165 |
237 |
206 |
267 |
|
240 |
75/125 |
98/161 |
34.9/22.3 |
583 |
0.70 |
3.06 |
1.71 |
97 |
155 |
310 |
490 |
140 |
191 |
185 |
226 |
|
300 |
60/100 |
80/130 |
43.8/28.0 |
602 |
0.72 |
3.06 |
1.88 |
95 |
153 |
300 |
490 |
126 |
163 |
174 |
203 |
|
400 |
47/78 |
64/102 |
57.3/36.6 |
627 |
0.75 |
4.29 |
2.08 |
92 |
150 |
290 |
480 |
113 |
141 |
164 |
184 |
|
500 |
36/60 |
51/81 |
72.3/46.2 |
654 |
0.79 |
4.29 |
2.30 |
90 |
149 |
290 |
470 |
105 |
124 |
158 |
171 |
|
630 |
28/47 |
42/64 |
91.2/58.3 |
726 |
0.87 |
4.29 |
2.53 |
87 |
145 |
280 |
460 |
97 |
110 |
151 |
160 |
Single Core 6.35/11KV (Um=12KV)
Single Core 8.7/15KV (Um=17.5kV)
Single Core 12.7/22KV (Um=24kV)
Single Core 19/33KV (Um=36kV)
Current Rating for 3.8/6.6KV (Um=7.2KV), 6.35/11KV (Um=12KV) & 8.7/15KV (Um=17.5KV)
Current Rating for 12.7/22KV (Um=24KV)
Current Rating for 19/33KV (Um=36KV)
Current Rating Conditions:
Ground Temperature:20°C
Ambient Temperature (air): 30°C
Depth of Soil: 0.8m
Thermal Resistance of Soil: 1.5K•m/W