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

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-
Section of Cables

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

0.271

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
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

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.
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

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
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

 

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)