Reference

Cable reference

The data behind the schedules — conductor properties, how XLPE compares with PVC, and the factors to apply when conditions differ from the standard case.

Specifying

What decides the cable

Seven things we need to size it

Maximum operating voltage and system earthing
Prospective fault level and required short circuit withstand
Load to be carried, plus any expected overload duration
Route length and permissible voltage drop
Installation method — buried, ducted, tray, conduit or free air
Ambient and ground temperature, soil thermal resistivity, grouping
Flame retardance, low smoke or halogen free requirements

Insulation

XLPE against PVC

PVC softens as it heats; XLPE is cross-linked and holds its form. That single difference is what lets XLPE run 20 °C hotter and carry more current in the same cross-section.

Property	PVC	XLPE
Nature	Thermoplastic — softens as it heats.	Thermosetting — cross-linked, holds its form.
Max. conductor temp.	70 °C continuous.	90 °C continuous.
Short circuit temp.	160 °C.	250 °C.
Current rating	Baseline.	Higher for the same cross-section.
Short circuit rating	Baseline.	Approximately 1.2 × PVC.
Insulation resistance	Baseline.	Substantially higher.
Moisture resistance	Moderate.	High.
Dielectric losses	Higher.	Low.
Diameter and bending	Larger diameter, larger bending radius.	Smaller diameter — less tray and duct space.
Service life	Good.	Longer, particularly where it runs warm.

IS 8130

Conductor data

Stranded conductors, class 2 — resistance and construction

21 sizes

Size (mm²)	Wires Cu	Wires Al	DC res. Cu (Ω/km)	DC res. Al (Ω/km)	AC res. 90 °C Cu	AC res. 90 °C Al
1.5	3	3	12.1	18.1	15.4	23.2
2.5	3	3	7.41	12.1	9.45	15.5
4	7	3	4.61	7.41	5.88	9.5
6	7	3	3.08	4.61	3.93	5.91
10	7	7	1.83	3.08	2.33	3.95
16	7	7	1.15	1.91	1.47	2.44
25	7	7	0.727	1.2	0.93	1.54
35	7	7	0.524	0.868	0.668	1.11
50	19	19	0.387	0.641	0.494	0.82
70	19	19	0.268	0.443	0.342	0.568
95	19	19	0.193	0.32	0.247	0.41
120	37	37	0.153	0.253	0.196	0.325
150	37	37	0.124	0.206	0.159	0.264
185	37	37	0.0991	0.164	0.128	0.211
240	61	37	0.0754	0.125	0.0985	0.161
300	61	61	0.0601	0.100	0.0796	0.129
400	61	61	0.0470	0.0778	0.0637	0.101
500	61	61	0.0366	0.0605	0.0515	0.0786
630	91	91	0.0283	0.0469	0.0421	0.0615
800	91	91	0.0221	0.0367	0.0354	0.0488
1000	91	91	0.0176	0.0291	0.0225	0.0372

Minimum number of wires for non-compacted stranded conductors to IS 8130 class 2. Sizes 1.5 to 10 mm² can also be supplied solid.

Correction

De-rating factors

Catalogue ratings assume 40 °C air and 30 °C ground. Multiply by the factor below for anything else; where cables are grouped, a grouping factor applies as well.

Ambient air temperature — cable in free air

Ambient	25 °C	30 °C	35 °C	40 °C	45 °C	50 °C	55 °C	60 °C
Factor	1.14	1.10	1.05	1.00	0.95	0.89	0.84	0.77

Ground temperature — buried direct or in duct

Ground	15 °C	20 °C	25 °C	30 °C	35 °C	40 °C	45 °C	50 °C
Factor	1.12	1.08	1.04	1.00	0.96	0.91	0.87	0.82

Maximum conductor temperature 90 °C for the XLPE range.

Specification

Standards the range is built to

IS 7098 Part 1

XLPE insulated cables for working voltages up to 1100 V

IS 694

PVC insulated cables for working voltages up to 1100 V

IS 8130 : 2013

Conductors for insulated electric cables and flexible cords

IS 5831 : 1984

PVC insulation and sheath of electric cables

IS 3975 : 1979

Galvanised steel wires, formed wires and tapes for armouring

IS 3961 Part 6

Recommended current ratings for PVC and XLPE insulated cables

IEC 60332-1-2

Flame propagation test for a single insulated conductor

BS 7671

Requirements for electrical installations — current rating tables