Power Copper Conductors According to IEC 60228

Tinned conductors

Cross section	cl.2	cl.5	Cross section	cl.2	cl.5
mm²	Ohm/km	Ohm/km	mm²	Ohm/km	Ohm/km
1.0	18.2	20	70	0.270	0.277
1.5	12.2	13.7	95	0.195	0.210
2.5	7.56	8.21	120	0.154	0.164
4	4.70	5.09	150	0.126	0.132
6	3.11	3.39	185	0.100	0.108
10	1.84	1.95	240	0.0762	0.0817
16	1.16	1.24	300	0.0607	0.0654
25	0.734	0.795	400	0.0475	0.0495
35	0.529	0.565	500	0.0369	0.0391
50	0.391	0.393	630	0.0286	0.0292

Plain conductors

Cross section	cl.2	cl.5	Cross section	cl.2	cl.5
mm²	Ohm/km	Ohm/km	mm²	Ohm/km	Ohm/km
1	18.1	19.5	70	0.268	0.272
1.5	12.1	13.3	95	0.193	0.206
2.5	7.41	7.98	120	0.153	0.161
4	4.61	4.95	150	0.124	0.129
6	3.08	3.30	185	0.0991	0.106
10	1.83	1.91	240	0.0754	0.0801
16	1.15	1.21	300	0.0601	0.0641
25	0.727	0.780	400	0.0470	0.0486
35	0.524	0.554	500	0.0366	0.0384
50	0.387	0.386	630	0.0283	0.0287

Correction factors according to IEC 60228

IEC 60228 standard provides electrical resistance of copper conductors at an ambient temperature of 20°C.

For other temperatures, correction factors are applied as below :

Temperature (°C)	Kt
5	1.064
10	1.042
15	1.020
20	1.000
25	0.980
30	0.962
35	0.943
40	0.926
45	0.909
50	0.893
55	0.877
60	0.862
65	0.847
70	0.833
75	0.820
80	0.806
85	0.794
90	0.781
95	0.769
100	0.758

Instrumentation & Control Conductors According to IEC 60092-376

	Tinned conductors		Plain conductors
Cross section	cl.2	cl.5	cl.2	cl.5
mm²	Ohm/km	Ohm/km	Ohm/km	Ohm/km
0.5	41.6	42.5	40.4	41.4
0.75	26.3	28.3	26.0	27.6
1	19.3	21.2	19.2	20.7
1.5	12.9	145.	12.8	14.1
2.5	8.02	8.71	7.56	8.47

Current Ratings for Continuous Service (IEC 60092-352)

Conductor temperature	90℃
Nominal cross-sectional Area	Single core		Two core		Three core & four core
mm²	A		A		A
0.5	10		8.5		7
0.75	13		11		9
1	18		15		13
1.5	23		20		16
2.5	30		26		21
4	40		34		28
6	52		44		36
10	72		61		50
16	96		82		67
25	127		108		89
35	157		133		110
50	196		167		137
70	242		206		169
95	293		249		205
120	339		288		237
150	389		331		273
185	444		377		311
240	522		444		366
300	601		511		420
	d.c.	a.c.	d.c.	a.c.	d.c.	a.c.
400	690	670	587	570	483	469
500	780	720	663	612	546	504
500	890	780	757	663	623	546

Note

1. Maximum permissible service temperature of the conductor is 90℃.

2. The current ratings given above are based on an ambient air temperature of 45℃.

3. The current ratings given above are for 6 cables of less bunched or laid together in flat formation. When more than 6 cables are bunched or laid close together, the current ratings given above should be multiplied by correction factor 0.85.

4. For cables with more than four core cables, the current ratings are calculated by the following formula :

I₁ : Current for single core cable

N : Number of cores

5. Correction factors for various ambient air temperature

Maximum conductor temperature	Correction factors for ambient air temperature
℃	35	40	45	50	55	60	65	70	75	80
90	1.10	1.05	1.00	0.94	0.88	0.82	0.74	0.67	0.58	0.47

Short Circuit Current Ratings

The short circuit currents quoted here are for cables operating normally at maximum conductor temperature of 90℃.

XLPE insulation is actually capable of withstanding short-term temperature up to 250℃.

According to ICEA P-32-382 Curves based on formula :

I : Short circuit current (kA)

A : Conductor area (mm²)

T₁ : Operating temperature (85℃)

T₂ : Short circuit temperature (250℃)

t : Short circuit duration (sec)

T1 = 90, T2 = 250

Nominal Area	Short Circuit Current(kA)
	Duration of Short Circuit in Second
(mm²)	0.03	0.05	0.07	0.1	0.14	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
1.5	1.26	0.98	0.83	0.69	0.58	0.49	0.40	0.35	0.31	0.28	0.26	0.24	0.23	0.22
2.5	2.02	1.56	1.32	1.10	0.93	0.78	0.64	0.55	0.49	0.45	0.42	0.39	0.37	0.35
4	3.25	2.52	2.13	1.78	1.50	1.26	1.03	0.89	0.80	0.73	0.67	0.63	0.59	0.56
6	4.86	3.77	3.18	2.66	2.25	1.88	1.54	1.33	1.19	1.09	1.01	0.94	0.89	0.84
10	8.19	6.34	5.36	4.49	3.79	3.17	2.59	2.24	2.01	1.83	1.70	1.59	1.50	1.42
16	12.99	10.06	8.50	7.11	6.01	5.03	4.11	3.56	3.18	2.90	2.69	2.52	2.37	2.25
25	20.6	15.9	13.5	11.3	9.5	8.0	6.5	5.6	5.0	4.6	4.3	4.0	3.8	3.6
35	28.5	22.1	18.7	15.6	13.2	11.1	9.0	7.8	7.0	6.4	5.9	5.5	5.2	4.9
50	38.6	29.9	25.3	21.2	17.9	15.0	12.2	10.6	9.5	8.6	8.0	7.5	7.1	6.7
70	55.9	43.3	36.6	30.6	25.9	21.6	17.7	15.3	13.7	12.5	11.6	10.8	10.2	9.7
95	77.5	60.0	50.7	42.4	35.9	30.0	24.5	21.2	19.0	17.3	16.0	15.0	14.1	13.4
120	97.9	75.8	64.1	53.6	45.3	37.9	31.0	26.8	24.0	21.9	20.3	19.0	17.9	17.0
150	120.3	93.1	78.7	65.9	55.7	46.6	38.0	32.9	29.5	26.9	24.9	23.3	22.0	20.8
185	150.8	116.8	98.8	82.6	69.8	58.4	47.7	41.3	36.9	33.7	31.2	29.2	27.5	26.1
240	198.3	153.6	129.8	108.6	91.8	76.8	62.7	54.3	48.6	44.3	41.0	38.4	36.2	34.3
300	248.7	192.6	162.8	136.2	115.1	96.3	78.6	68.1	60.9	55.6	51.5	48.2	45.4	43.1
400	329.3	255.1	215.6	180.4	152.5	127.6	104.1	90.2	80.7	73.6	68.2	63.8	60.1	57.0
500	401.0	310.6	262.5	219.6	185.6	155.3	126.8	109.8	98.2	89.7	83.0	77.7	73.2	69.5

Reactance / Impedance

Reactance

Conductor area	mm²	1.5	2.5	4	6	10	25	35	50	70	95	120	150	185	240	300
Rating factors	Ω /km	0.135	0.125	0.117	0.111	0.103	0.098	0.097	0.094	0.091	0.090	0.088	0.088	0.088	0.088	0.087

The reactance of a cable operating in AC system depends on many factors, including, in particular, the axial spacing between conductors and proximity and magnetic properties of adjacent steelwork. The formar is known for multicore cable, but may vary for single core cables depending upon the spacing between them and their disposition when installed.

Reactances of cables in certain dispositions remote from steelwork are calculable and are shown. The tabulated values are for cables with circular conductors. The value for a sector- shaped conductor should be taken as 90% of the tabulated value. The value of reactance so calculated is for a supply frequency of 60Hz. For any other frequency, a correction should be made in direct proportion to the frequency.

For example at 50Hz, the reactance is 0.83 times that at 60Hz. Induction for 2-and 3- conductor cables is given by the formula :

L = Inductance in H/m and phase

a = Axial space between conductor

d = Conductor diameter in mm

Reactance for 2- and 3- conductor cables is given by the formula :

X = Reactance in ohm per phase

F = Frequency in Hz

L = Inductance in H/m and phase

I = Conductor Iength in meter

Impedance

Conductor area	mm²	1.5	2.5	4	6	10	16	25	35	50	70	95	120	150	185	240	300
Rating factors	Ω/km	15.557	9.641	5.994	3.967	2.348	1.482	0.941	0.681	0.507	0.356	0.265	0.215	0.183	0.155	0.131	0.116

Impedance for 2, 3 & 4 conductor cables is given by the formula :

Z = Impedance in ohm per phase

R = Resistance at operating temp. in ohm per phase

X = Reactance in ohm per phase

Voltage Drop (Cables Up to 1 KV)

Nominal c.s.a mm²	K
	3x1 cores (trefoil formation)		2 cores		3-4 cores
	C.d.T. c.a. cosfi 1 mV/Am	C.d.T. c.a. cosfi 0.8 mV/Am	C.d.T. c.a. cosfi 1 mV/Am	C.d.T. c.a. cosfi 0.8 mV/Am	C.d.T. c.a. cosfi 1 mV/Am	C.d.T. c.a. cosfi 0.8 mV/Am
1			46.4	37.3	40.1	32.3
1.5			31.1	25.0	26.9	21.7
2.5			19.3	15.6	16.7	13.5
4			12.0	9.73	10.4	8.41
6			7.93	6.48	6.860	5.60
10	3.51	2.90	4.69	3.88	4.059	3.35
16	2.21	1.86	2.96	2.48	2.559	2.15
25	1.40	1.21	1.87	1.61	1.620	1.39
35	1.01	0.891	1.35	1.19	1.168	1.03
50	0.747	0.681	0.998	0.910	0.864	0.787
70	0.517	0.494	0.690	0.660	0.597	0.571
95	0.374	0.379	0.500	0.507	0.432	0.439
120	0.296	0.316	0.396	0.422	0.343	0.365
150	0.244			0.273	0.282	0.316
185	0.195			0.234	0.225	0.271
240	0.151			0.198	0.174	0.229
300	0.122			0.175	0.142	0.203

Voltage Drop Coefficient

The voltage drop coefficients in each circuit are given in the following table :

Voltage	Conductor size	Voltage drop coefficient
	mm²	100	95	90	85	80	75	70
250V	0.75	1.00	0.95	0.90	0.85	0.80	0.75	0.70
	1	1.00	0.95	0.90	0.85	0.80	0.75	0.70
0.6/1KV	1.5	1.00	0.95	0.90	0.85	0.80	0.75	0.71
	2.5	1.00	0.95	0.90	0.86	0.81	0.76	0.71
	4	1.00	0.96	0.91	0.86	0.81	0.76	0.71
	6	1.00	0.96	0.91	0.86	0.81	0.77	0.72
	10	1.00	0.96	0.92	0.87	0.82	0.77	0.73
	16	1.00	0.97	0.92	0.88	0.83	0.76	0.74
	25	1.00	0.98	0.94	0.90	0.85	0.81	0.76
	35	1.00	0.99	0.95	0.91	0.87	0.83	0.78
	50	1.00	1.00	0.97	0.93	0.89	0.85	0.81
	70	1.00	1.02	1.00	0.97	0.93	0.90	0.86
	95	1.00	1.04	1.03	1.01	0.98	0.95	0.92
	120	1.00	1.07	1.06	1.05	1.03	1.00	0.97
	150	1.00	1.09	1.10	1.09	1.08	1.05	1.03
	185	1.00	1.13	1.15	1.15	1.15	1.13	1.11
	240	1.00	1.19	1.23	1.25	1.25	1.25	1.24
	300	1.00	1.24	1.31	1.35	1.36	1.37	1.37