What is the difference between Class 2 and Class 5 conductors?

Class 2 is a stranded conductor for fixed installations, while Class 5 is a flexible conductor made of finer wires, intended for flexible cables and cords (Clause 4).

What is the maximum DC resistance for a 4 sq mm plain copper conductor?

4.61 ohms/km at 20°C (Table 4).

How is conductor resistance measured at the site corrected to 20°C?

Using the formula R₂₀ = Rt / [1 + 0.00393(t-20)], where Rt is the resistance at temperature 't' °C (Clause 8.3).

Does this standard cover aluminium conductors?

No, this standard is exclusively for copper and copper alloy conductors. Aluminium conductors are covered in IS 8130's counterpart, IS 8130.

IS 8130

: 1984

Conductors for insulated electric cables and flexible cords - Copper and copper alloy conductors

CurrentEssentialSpecificationBIMMaterials Science · Electrical Installations

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This standard specifies the requirements for solid (Class 1), stranded (Class 2), and flexible (Class 5 & 6) copper conductors used in a wide variety of insulated electrical cables and cords. It defines material properties, constructional details, dimensions, and essential electrical (resistance) and mechanical (tensile/elongation) characteristics.

Specifies requirements for copper and copper alloy conductors used in insulated electric cables and flexible cords.

Quick Reference Values

Maximum volume resistivity of annealed copper at 20°C0.017241 Ω·mm²/m

Temperature coefficient of resistance for copper per °C at 20°C0.00393

Minimum elongation at break for annealed copper wire (>0.5mm dia)15%

Maximum DC resistance for 1 sq mm plain copper conductor at 20°C18.1 Ω/km

Key Formulas

R₂₀ = Rt * [1 / (1 + α(t - 20))] — Resistance correction to 20°C

Practical Notes

This code is the foundation for the conductor part of most Indian cable standards (like IS 694, IS 1554). Always check the specific cable standard for the required conductor class.

Verifying the DC resistance (as per Table 4) is the most critical quality check for conductors. Field measurements must be corrected to the standard reference temperature of 20°C.

The 'Class' of the conductor (1, 2, 5, or 6) determines its flexibility. Class 1/2 are for fixed wiring, while Class 5/6 are for flexible cords and applications requiring movement.