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-
Section of Cables mm²

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
Cconductor

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
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance  at
20℃

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
Cconductor

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
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance
at 20℃

Total Cross Section

Max. DC Resistance  at
20℃

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.
Cross- Section Area

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
Resistance CU / AL

A C
Resistance CU / AL

Short Circuit Rating of Conductor CU / AL
1 sec

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