Standard low voltage underground cable

Low-voltage underground cable is an electric cable placed underground, used to transmit voltage up to 1kV and is specified in TCVN 5935-1:2013, TCVN 7997:2009. Inside:

TCVN 5935-2:2013 regulates the structure of production of electric cables and test methods;
TCVN 7997:2009 specifies the method of installation.

TCVN 5935-1:2013 regulates structure of low voltage underground cables

1. Rated voltage

The rated voltages Uo/U(Um) of the cables considered in this standard are 0.6/1 (1.2) kV and 1.8/3 (3.6) kV.

2. Insulating compound

Insulating compound	Shortened symbol
a) Thermoplastics.Polyvinyl chloride is used for cables with rated voltage Uo/U £1.8/3 kV	PVC/A*
b) Horizontal linkEthylene propylene rubber or the like (EPM or EPDM) Molecular rubber or ethylene propylene rubber with high hardness Cross-linked polyethylene	EPR HEPR XLPE
* Polyvinyl chloride based insulating compounds used for cables with rated voltage Uo/U = 3.6/6 kV are denoted PVC/B in IEC 60502-2.

The highest conductor temperatures for the different classes of insulating compounds covered by this standard are given in the table below:

Insulating compound			Maximum conductor temperature 0C
			Work as usual		Short circuit (longest time is 5s)
Polyvinyl chloride	(PVC/A)Cross section of conductor £300 mm2. Cross section of conductor >300 mm2.	70 70		160 140
Cross-linked polyethylene	(XLPE)	90		250
Ethylene propylene rubber	(EPR and HEPR)	90		250

3. Coating compound

Coating compound

Shortened symbol

The highest temperature of conductor in normal operation
0C

a) ThermoplasticsPolyvinyl chloride (PVC)

Polyethylene

Halogen-free

b) Elastic material

Polychloroprene, polyethylene chlorosulfonate or similar polymers

ST1

ST2

ST3

ST7

ST8

SE1

4. Conductor

Conductors shall be class 1 or class 2 of uncoated or coated annealed copper or of aluminum or aluminum alloy or class 5 of uncoated or coated copper in accordance with IEC 60228.

5. Insulation

a. Insulating materials; The insulation shall be an extruded dielectric of one of the two classes listed in the first Table.

b. PVC/A . insulation thickness

Nominal cross-sectional area of conductor mm2	Nominal thickness of insulation at rated voltage Uo/U (Um)
	0.6/1 (1.2) kV mm2	1.8/3 (3.6) kV mm2
1.5 and 2.54 and 6 10 and 16 25 and 35 50 and 70 95 and 120 150 185 240 300 400 500 to 800 1 000 won	0.81.0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0	–– 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.4 2.6 2.8 3.0
NOTE It is not recommended to use conductors with cross-sections less than the values given in this table.

c. Insulation thickness XLPE

Nominal cross-sectional area of conductor mm2	Nominal thickness of insulation at rated voltage Uo/U (Um)
	0.6/1 (1.2) kV mm2	1.8/3 (3.6) kV mm2
1.5 and 2.54 and 6 10 and 16 25 and 35 50 70 and 95 120 150 185 240 300 400 500 630 800 1 000 won	0.70.7 0.7 0.9 1.0 1.1 1.2 1.4 1.6 1.7 1.8 2.0 2.2 2.4 2.6 2.8	–– 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.2 2.4 2.6 2.8
NOTE It is not recommended to use conductors with cross-sections less than the values given in this table.

d. Insulation Thickness EPR/HEPR

Nominal cross-sectional area of conductor mm2	Nominal thickness of insulation at rated voltage Uo/U (Um)
	0.6/1 (1.2) kV mm2		1.8/3 (3.6) kV mm2
	EPRmm	HEPRmm	EPRmm	HEPRmm
1.5 and 2.54 and 6 10 and 16 25 and 35 50 70 95 120 150 185 240 300 400 500 630 800 1 000 won	1.01.0 1.0 1.2 1.4 1.4 1.6 1.6 1.8 2.0 2.2 2.4 2.6 2.8 2.8 2.8 3.0	0.70.7 0.7 0.9 1.0 1.1 1.1 1.2 1.4 1.6 1.7 1.8 2.0 2.2 2.4 2.6 2.8	–– 2.2 2.2 2.2 2.2 2.4 2.4 2.4 2.4 2.4 2.4 2.6 2.8 2.8 2.8 3.0	–– 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.2 2.4 2.6 2.8
NOTE It is not recommended to use conductors with cross-sections less than the values given in this table.

6. Multi-core cable assembly, inner sheath and filler

a. Inner coating and filler

The inner wrap can be extruded or wound. For cables with round cores, except cables with more than five cores, a wound inner covering is allowed only if the space between the cores is substantially filled.

The material used for the inner covering and filler shall be suitable for the operating temperature of the cable and compatible with the insulating material.

Extrusion inner coating thickness

Assumed diameter of arranged core

Thickness of extruded inner coating (approximate value)
mm

Larger than
mm

To and equal to
mm

–25

2535

–

1.01.2

1.4

1.6

1.8

2.0

Thickness of wrapped inner layer

The approximate thickness of the wound inner covering shall be 0.4 mm for the assumed diameter of the arranged core up to and including 40 mm and 0.6 mm for larger diameters.

7. Metal curtain

The metal screen shall be one or more ribbons, or a woven mesh or a layer of concentric wire, or a combination of wires and ribbon(s).

8. Metal armor

The types of armor covered by this standard are as follows:

flat wire or round wire armor: Round wire or flat wire shall be galvanized steel, tinned copper or copper, aluminum or aluminum alloy.
dual-strip armour: The ribbon must be steel, galvanized steel, aluminum, or aluminum alloy. Steel strip shall be hot-rolled or cold-rolled of commercial quality.

NOTE For cables of rated voltage 0.6/1 (1,2) kV with a cross-sectional area exceeding 6 mm2, armor can be provided in the form of a woven galvanized steel wire mesh according to the agreement. agreement between manufacturer and purchaser.