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Maximum DC Conductor Resistance (IEC 60228)

This reference provides maximum DC resistance values for Class 2 stranded conductors at 20°C, together with calculated reference values at 90°C.

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Conductor Data Table

Type a size (e.g. “240”) to filter the table:

Nominal Area (mm²)	Verified Conductor Diameter (mm)	Copper @ 20°C (Ω/km)	Copper @ 90°C (Ω/km)	Aluminium @ 20°C (Ω/km)	Aluminium @ 90°C (Ω/km)
0.5		36.0	45.9
0.75		24.5	31.2
1.0		18.1	23.1
1.5		12.1	15.4
2.5		7.41	9.45
4		4.61	5.88
6		3.08	3.93
10		1.83	2.33	3.08	3.95
16		1.15	1.47	1.91	2.45
25		0.727	0.927	1.20	1.54
35		0.524	0.668	0.868	1.11
50	8.16	0.387	0.494	0.641	0.822
70	9.90	0.268	0.342	0.443	0.568
95	11.35	0.193	0.246	0.320	0.410
120	12.83	0.153	0.195	0.253	0.324
150	13.95	0.124	0.158	0.206	0.264
185	16.40	0.0991	0.126	0.164	0.210
240	17.95	0.0754	0.0961	0.125	0.160
300	20.5	0.0601	0.0766	0.100	0.128
400	23.5	0.0470	0.0599	0.0778	0.0997
500	26.40	0.0366	0.0467	0.0605	0.0776
630	30.8	0.0283	0.0361	0.0469	0.0601
800		0.0221	0.0282	0.0367	0.0471
1000	38.4	0.0176	0.0224	0.0291	0.0373
1200	44.0	0.0151	0.0193	0.0247	0.0317
1400		0.0129	0.0164	0.0212	0.0272
1600	50.3	0.0113	0.0144	0.0186	0.0238
1800		0.0101	0.0129	0.0165	0.0212
2000		0.0090	0.0115	0.0149	0.0191
2500		0.0072	0.0092	0.0127	0.0163

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Technical Notes

• Resistance values at 20°C are IEC 60228 Class 2 stranded conductor maximum DC resistance values
• Values at 90°C are calculated using standard temperature correction factors
• Typical multipliers:
  • Copper ≈ ×1.275
  • Aluminium ≈ ×1.282
• Values represent DC resistance only

• They do not include AC effects such as skin effect, proximity effect or frequency dependent losses

• Verified conductor diameters are included only where sourced from manufacturer or utility data

• IEC does not define exact diameters for smaller Class 2 conductors

• For larger sizes (typically ≥1200 mm²), conductors may be segmented (Milliken construction) and must be treated as manufacturer specific

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Terminations and Installation Risk

• Termination selection must be based on actual verified conductor diameter and construction
• Aluminium conductors require bimetallic terminations

• DNO compliant shear bolt connectors are recommended

• Sectorial, shaped and segmented conductors require specialist termination design
• Crimping aluminium and non circular conductors carries elevated installation risk

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Disclaimer

This information is provided for general technical reference only.

All values must be independently verified against:

• applicable standards
• cable manufacturer data
• accessory manufacturer data
• project specifications
• local and international regulations

DC resistance values do not represent full system behaviour including AC impedance, reactance or transient effects.

No liability is accepted for any loss, damage or application arising from use of this information.

Specifications, conductor constructions and manufacturer data may change without notice.