Medium Voltage Cables 

Medium Voltage Cables to IEC 60502

Three Core Cables to IEC 60502

Application
The three core cables are designed for distribution of electrical power with nominal voltage Uo/U ranging from 1.8/3KV to 26/35KV 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
IEC 60502 Part 1(1.8/3KV)
IEC 60502 Part 2(3.6/6KV to 18/30KV)

Construction

Conductor: Plain annealed copper or aluminium complying with IEC 60228 class 1 or 2.
Conductor Screen: The conductor screen consists of an extruded layer of non metallic, semi-conducting compound applied on top of a semi-conducting tape. The conductor screen is applied under triple extrusion process over the conductor along with the insulation and the insulation screen. The extruded semi-conducting compound is firmly bonded to the insulation to exclude all air voids and can be easily hand stripped on site. The conductor screen is not necessary for both PVC and EPR/HEPR insulated 1.8/3.6KV and 3.6/6KV cables.
Insulation: Insulation is of polyvinyl chloride (PVC) intended for 1.8/3.6KV and 3.6/6KV cables, cross-linked polyethylene compound (XLPE) or ethylene propylene rubber (EPR/ HEPR).
Table 1. Insulation Thickness Of XLPE Or EPR/HEPR Insulation

Nom. Cross
Section Area

 

Insulation Thickness at Nom. Voltage

1.8/3kV
(Um=3.6)kV

3.6/6kV
(Um=7.2)kV

6/10KV
(Um=12KV)

8.7/15KV
(Um=17KV)

12/20KV
(Um=24KV)

18/30KV
(Um=36KV)

21/35KV
(Um=42KV)

26/35KV
(Um=42KV)

mm2

mm

mm

mm

mm

mm

mm

mm

mm

 

XLPE/EPR

XLPE

EPR

XLPE/EPR

XLPE/EPR

XLPE/EPR

XLPE/EPR

XLPE/EPR

XLPE/EPR

 

Unscreened

Screened

10

2.0

2.5

3.0

2.5

-

-

-

-

-

-

16

2.0

2.5

3.0

2.5

3.4

-

-

-

-

-

25

2.0

2.5

3.0

2.5

3.4

4.5

-

-

-

-

35

2.0

2.5

3.0

2.5

3.4

4.5

5.5

-

-

-

50 – 185

2.0

2.5

3.0

2.5

3.4

4.5

5.5

8.0

9.3

10.5

240

2.0

2.6

3.0

2.6

3.4

4.5

5.5

8.0

9.3

10.5

300

2.0

2.8

3.0

2.8

3.4

4.5

5.5

8.0

9.3

10.5

400

2.0

3.0

3.0

3.0

3.4

4.5

5.5

8.0

9.3

10.5

500 - 1600

2.2-2.8

3.2

3.2

3.2

3.4

4.5

5.5

8.0

9.3

10.5

Insulaton Screen: The insulation screen consists of an extruded layer of non metallic, semi-conducting compound extruded over the insulation of each core. 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 individual cores or core assembly 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. The insulation screen is not necessary for both PVC and EPR/HEPR insulated 1.8/3.6KV and 3.6/6KV cables. The screen may be covered by semi-conductive water blocking swellable tape to ensure longitudinal watertightness.
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 and fillers are made of non hygroscopic material like polypropylene, except if the cable is to be made longitudinally watertight. The inner covering is extruded in general but may be lapped if the interstices between the cores are filled.
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 0.4mm for fictitious diameters over the laid up cores up to and including 40mm and 0.6mm for larger diameter.

Metallic Layer: The metallic layer may be applied over the individual cores or the core assembly collectively. The following types of metallic layers are provided:
1) Metallic Screen
2) Concentric Conductor
3) Metallic Sheath
4) Metallic Armour
The metallic screen shall consist of either copper tapes or a concentric layer of copper wires or a combination of tapes and wires. The concentric conductor is applied directly over the inner covering. The metallic sheath consists of lead or lead alloy applied as a tightly fitting seamless tube. The metallic armour consists of either flat wire armour, round wire armour, and double tape armour.
Table 3. Minimum Total Cross Section Of Metallic Screen

Nom. Cross-Section
Area of Cable

Min. Cross-Section of Metallic Screen

DC Resistance of the Copper Wire Screen

mm²

mm²

mm

up to 120

16

1.06

150-300

25

0.72

400-630

35

0.51

800-1000

50

0.35

Separation Sheath (for armoured cable): The separation sheath comprises a layer of extruded PVC, PE or  LSZH applied over the laid up cores under the armour. PVC is normally of grade ST2 and PE of grade ST7. The nominal thickness is calculated by 0.02Du + 0.6mm where Du is the fictitious diameter under the sheath in mm. For cables without a lead sheath, the nominal separation sheath thickness shall not be less than 1.2mm. For cables where the separation sheath is applied over the lead sheath, the nominal separation sheath thickness shall not be less than 1.0mm.
Tabel 4. Separation Thickness

Cores Diameter

Approx. Thickress of
Inner Sheath

mm

mm

> 

< 

 

35

45

1.4

45

60

1.6

60

80

1.8

80

-

2.0

Lapped Bedding (for armoured lead sheathed cable): The lapped bedding applied to the lead sheath consists of either impregnated/synthetic compounded paper tapes or a combination of two layers of these paper tapes followed by a few layers of compounded fabulous materials. The thickness is around 1.5mm.
Armour (for armoured cable): The armour is applied over the inner covering helically. It consists of either flat galvanized steel wire armour (strip), round galvanized steel wire armour, and double steel tape armour.
Table 5. Round Armour Wire Diameter

Fictitious Diameter Under the Armour

Armour Wire Diameter

mm

mm

> 

< 

 

-

10

1.25

10

15

1.25

15

25

1.6

25

35

2.0

35

60

2.5

60

-

3.15

Table 6. Armour Tape Thickness

Fictitious Diameter Under the Armour

Galvanized Steel / Steel

Aluminum / Aluminium Alloy

mm

mm

mm

> 

< 

 

 

-

30

0.2

0.5

30

70

0.5

0.5

70

-

0.8

0.8

For flat wire armour and fictitious diameter under the armour greater than 15mm, the nominal thickness of the flat steel wire diameter shall be 0.8mm.Cables with fictitious diameter under the armour up to and including 15mm, flat wire armour will not be used. The tape armour is applied helically in two layers so that the outer tape is approximately central over the gap of the inner tape. If tape armour is used, the inner covering shall be reinforced by taped bedding.
Over Sheath: Overall sheath comprises a layer of extruded either thermoplastic compound (PVC ST3 type or PE ST7 type) or elastomeric compound (polychlorprene CSP or chlorosulfonated PE). The nominal oversheath thickness is calculated by 0.035D+1 where D is the fictitiuous diameter immediately under the oversheath in mm. For unarmoured cables and cables with the oversheath not applied over the armour, metallic screen or concentric conductor, the nominal oversheath thickness shall not be less than 1.4mm. And for cables with oversheath applied over the armour, metallic screen or concentric conductor, the nominal oversheath thickness shall not be less than 1.8mm.

PHYSICAL PROPERTIES:
Operating Temperature: up to 70°C (PVC insulation); up to 90°C (XLPE or EPR insulation)
Temperature Range: -5°C ( PVC sheath ); -20°C ( PE sheath )
Short Circuit Temperature( 5 seconds maximum duration ): 140-160 °C (PVC insulation);
250°C (XLPE or EPR insulation)
Bending Radius: 15 x OD
Table 7. Nominal /Operating /Testing Voltages

Rated Voltage Uo/U

Operating Voltage (Um)

Testing Voltage (rms)

1.8/3KV

3.6KV

6.5KV

3.6/6KV

7.2KV

12.5KV

6/10KV

12KV

21KV

8.7/15KV

17.5KV

30.5KV

12/20KV

24KV

42KV

18/30KV

36KV

63KV

21/35KV

42KV

73.5(53)*KV

26/35KV

42KV

91(65)*KV

*21/35KV and 26/35kV power frequency voltage test can be made under the following conditions: 2.5Uo x 30mins or 3.0Uo x 15mins. Numbers in brackets refer to the test values for 3.0Uo x 1.5mins.

Three Core 1.8/3KV (Um=3.6KV) Dimensional Data

 

 

Unarmoured Cables

Steel Round-Wire Armoured Cables

Nom.
Cross-
Section
Area

Nom.Insulation
Thickness

Copper
Tape
Thickness

Copper
Wire
Screen
Area*

Nom.
Sheath
Thickness

Approx.
Overall
Diameter

Approx.
Weight

Nom.
Bedding
Thickness

Armour
Wire
Size

Nom.
Sheath
Thickness

Approx.
Overall
Diameter

Approx.
Weight

CU

AL

CU

AL

mm2

mm

mm

mm2

mm

mm

kg/km

mm

mm

mm

mm

kg/km

10

2.0

0.1

16

1.8

23

650

460

1.2

1.6

1.8

28

1480

1290

16

2.0

0.1

16

1.8

24

840

540

1.2

1.6

1.9

29

1720

1410

25

2.0

0.1

16

1.8

26

1160

680

1.2

1.6

1.9

32

2130

1650

35

2.0

0.1

16

1.8

29

1490

820

1.2

2.0

2.1

36

2810

2140

50

2.0

0.1

16

1.9

32

1900

1000

1.2

2.0

2.2

39

3340

2450

70

2.0

0.1

16

2.0

36

2580

1290

1.2

2.0

2.3

42

4200

2910

95

2.0

0.1

16

2.2

40

3440

1640

1.3

2.5

2.4

47

5620

3820

120

2.0

0.1

16

2.3

43

4220

1950

1.3

2.5

2.5

51

6580

4310

150

2.0

0.1

25

2.4

46

5090

2290

1.4

2.5

2.7

54

7680

4870

185

2.0

0.1

25

2.5

50

6240

2730

1.5

2.5

2.8

58

9060

5560

240

2.0

0.1

25

2.7

56

8030

3430

1.6

2.5

3.0

64

11200

6600

300

2.0

0.1

25

2.8

60

9890

4100

1.6

2.5

3.1

69

13590

7500

400

2.0

0.1

35

3.1

68

12530

5150

1.8

3.15

3.4

78

17260

9880

500

2.2

0.1

35

3.3

75.7

16680

7510

1.8

3.15

3.5

84.3

21780

13025

630

2.4

0.1

35

3.5

84.9

21770

10040

1.8

3.15

3.8

94.6

27400

16050

*Optional wire screen can be provided in combination of copper tapes. Nominal screen area, as stated in the table, can be supplied as standard.

 

Steel Flat Wire Armoured Cables

Double Steel Tape Armoured Cables

Nom.
Cross-
Section
Area

Nom.
Bedding
Thickness

Armour
Wire
Size

Nom.Sheath
Thickness

Approx.
Overall
Diameter

Approx.
Weight

Nom.
Bedding
Thickness

No of Steel Tapes x Nom Tape
Thickness

Nom.Sheath
Thickness

Approx.
Overall
Diameter

Approx.
Weight

CU

AL

CU

AL

mm2

mm

mm

mm

mm

kg/km

mm

mm

mm

mm

kg/km

10

1.2

0.8

1.8

24.5

1245

1065

1.2

2 x 0.2

1.8

23.6

925

750

16

1.2

0.8

1.8

27.1

1565

1280

1.2

2 x 0.2

1.8

26.2

1205

925

25

1.2

0.8

1.8

29.7

1975

1525

1.2

2 x 0.2

1.9

29.0

1590

1145

35

1.2

0.8

1.9

32.5

2420

1805

1.2

2 x 0.2

1.9

31.6

1985

1370

50

1.2

0.8

2.0

35

2860

2080

1.2

2 x 0.2

2.0

34.1

2400

1605

70

1.2

0.8

2.1

38.7

3685

2525

1.2

2 x 0.5

2.2

39.5

3570

2410

95

1.3

0.8

2.2

42.9

4695

3080

1.3

2 x 0.5

2.3

43.7

4570

2950

120

1.3

0.8

2.3

46.4

5650

3585

1.3

2 x 0.5

2.4

46.1

5510

3440

150

1.4

0.8

2.4

49.6

6630

4085

1.4

2 x 0.5

2.6

50.6

6500

3955

185

1.5

0.8

2.6

54.1

7990

4820

1.5

2 x 0.5

2.7

54.9

7825

4650

240

1.6

0.8

2.7

59.2

10060

5790

1.6

2 x 0.5

2.8

60.0

9825

5600

300

1.6

0.8

2.9

64.6

12230

6865

1.6

2 x0.5

3.0

65.4

12030

6660

400

1.8

0.8

3.1

71.0

15200

8280

1.8

2 x 0.5

3.2

71.8

14970

8055

500

1.8

0.8

3.3

79.5

19090

10255

1.8

2 x 0.8

3.5

80.5

18880

10035

630

1.8

0.8

3.6

89.8

24400

12920

1.8

2 x 0.8

3.8

92.3

25070

13620

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 Copper Wire Screen Per Core
1 sec

Short Circuit Rating of Copper Tape Screen Per Core
1 sec

Reactance

Inductance

mm²

µΩ/m

µΩ/m

kA

pF/m

mA/m

kA

kA

µΩ/m

nH/m

10

1830/3080

2330/3920

1.4/0.9

160

0.25

2.6

0.4

101

390

16

1150/1910

1460/2420

2.2/1.4

180

0.27

2.6

0.4

98

370

25

727/1200

929/1538

3.6/2.3

220

0.29

2.6

0.4

95

350

35

524/868

668/1113

5.0/3.2

250

0.31

2.6

0.5

92

330

50

387/641

494/822

6.8/4.4

270

0.33

2.6

0.5

88

310

70

268/443

343/568

9.8/6.3

310

0.35

2.6

0.6

84

290

95

193/320

248/410

13.3/8.5

350

0.38

2.6

0.6

81

270

120

153/253

196/325

17.2/11.0

380

0.46

2.6

0.7

79

250

150

124/206

159/265

21.2/13.5

420

0.50

2.6

0.7

77

260

185

99.1/164

128/211

26.6/17.0

460

0.56

2.6

0.8

76

250

240

75.4/125

98/161

34.9/22.3

510

0.61

4.3

0.9

74

240

300

60.1/100

80/130

43.8/28.0

570

0.68

4.3

1.0

73

250

400

47.0/77.8

64/102

57.3/36.6

590

0.70

5.8

1.1

71

240

500

36.6/60.5

57/81

72.3/46.2

610

0.72

5.8

1.2

69

230

630

28.3/46.9

42/64

91.2/58.3

630

0.74

5.8

1.3

67

220

Three Core 3.8/6.6KV (Um=7.2KV)
Three Core 6/10KV (Um=12KV)
Three Core  8.7/15KV (Um=17.5KV)
Three Core 12/20KV (Um=24KV)
Three Core 18/30KV (Um=36KV)
Three Core 21/35KV (Um=42KV)
Three Core 26/35KV (Um=42KV)
Current Rating for Three Core 1.8/3KV(Um=7.2 )KV to 26/35KV(Um=42KV)

Current Rating Conditions:

Ground Temperature: 20°C Ambient Temperature (air): 30°C Depth of Soil: 0.8 m
Thermal Resistance of Soil: 1.5K•m/W