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 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 18/30KV 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)
mm² mm mm mm mm mm mm
  XLPE/EPR XLPE EPR XLPE/EPR XLPE/EPR XLPE/EPR XLPE/EPR
  Unscr
eened
Scre
ened
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
240 2.0 2.6 3.0 2.6 3.4 4.5 5.5 8.0
300 2.0 2.8 3.0 2.8 3.4 4.5 5.5 8.0
400 2.0 3.0 3.0 3.0 3.4 4.5 5.5 8.0
500 - 1600 2.2-2.8 3.2 3.2 3.2 3.4 4.5 5.5 8.0

 

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 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 4.8 8.2 101 390
16 1150/1910 1460/2420 2.2/1.4 180 0.27 4.8 8.2 98 370
25 727/1200 929/1538 3.6/2.3 220 0.29 4.8 8.2 95 350
35 524/868 668/1113 5.0/3.2 250 0.31 4.8 8.2 92 330
50 387/641 494/822 6.8/4.4 270 0.33 4.8 8.2 88 310
70 268/443 343/568 9.8/6.3 310 0.35 4.8 8.2 84 290
95 193/320 248/410 13.3/8.5 350 0.38 4.8 8.2 81 270
120 153/253 196/325 17.2/11.0 380 0.46 4.8 8.2 79 250
150 124/206 159/265 21.2/13.5 420 0.50 4.8 8.2 77 260
185 99.1/164 128/211 26.6/17.0 460 0.56 4.8 8.2 76 250
240 75.4/125 98/161 34.9/22.3 510 0.61 4.8 8.2 74 240
300 60.1/100 80/130 43.8/28.0 570 0.68 4.8 8.2 73 250
400 47.0/77.8 64/102 57.3/36.6 590 0.70 4.8 8.2 71 240
500 36.6/60.5 57/81 72.3/46.2 610 0.72 4.8 8.2 69 230
630 28.3/46.9 42/64 91.2/58.3 630 0.74 4.8 8.2 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)
Current Rating for Three Core 3.6/6KV(Um=7.2 )KV to 18/30KV(Um=36KV)

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