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Fire Resisting Cables

Current Rating and Voltage Drop

Multi-Core Cables having XLPE Insulation, Unarmoured (Copper Conductor) 600/1000V

 

 

 

Current-Carrying Capacities (Amp) XLPE/PVC Cables :

Size of Conductor	Reference Method 4 (Enclosed in conduit and insulated wall etc)		Reference Method 3 (Enclosed in conduit on a wall or cell, or in trunking)		Reference Method 1 (Clipped direct)		Reference Method 11 (on a perforated cable tray) or Reference Method 13 (free air)
	1 2-core cable 1-phase ac or dc	1 3- or 4-core cable 3-phase ac	1 2-core cable 1-phase ac or dc	1 3- or 4-core cable 3-phase ac	1 2-core cable 1-phase ac or dc	1 3- or 4-core cable 3-phase ac	1 2-core cable 1-phase ac or dc	1 3- or 4-core cable 3-phase ac
1 mm²	2 A	3 A	4 A	5 A	6 A	7 A	8 A	9 A
1.5	18.5	16.5	22	19.5	24	22	26	23
2.5	25	22	30	26	33	30	36	32
4	33	30	40	35	45	40	49	42
6	42	38	51	44	58	52	63	54
10	57	51	69	60	80	71	86	75
16	76	68	91	80	107	96	115	100
25	99	89	119	105	138	119	149	127
35	121	109	146	128	171	147	185	158
50	145	130	175	154	209	179	225	192
70	183	164	221	194	269	229	289	246
95	220	197	265	233	328	278	352	298
120	253	227	305	268	382	322	410	346
150	290	259	334	300	441	371	473	399
185	329	295	384	340	506	424	542	456
240	386	346	459	398	599	500	641	538
300	442	396	532	455	693	576	741	621
400	-	-	625	536	803	667	865	741

Note: Rating factors for ambient temperature other than 30℃ please refer Table C

Rating factors for ground temperature other than 15℃ please refer Table D

Group Rating Factor please refer to Table F & Table G

Voltage Drop (Per Amp Per Meter) XLPE/PVC Cables :

Size of Conductor	2-core cable dc	2-core cable 1-phase ac			3- or 4-core cable 3-phase ac
1 mm²	2 mV/A/m	3 mV/A/m			4 mV/A/m
1.5	31	31			27
2.5	19	19			16
4	12	12			10
6	7.9	7.9			6.8
10	4.7	4.7			4
16	2.9	2.9			2.5
		r	x	Z	r	x	z
25	1.85	1.85	0.16	1.9	1.6	0.14	1.65
35	1.35	1.35	0.155	1.35	1.15	0.135	1.15
50	0.98	0.99	0.155	1.00	0.86	0.135	0.87
70	0.67	0.67	0.150	0.69	0.59	0.130	0.60
95	0.49	0.50	0.150	0.52	0.43	0.130	0.45
120	0.39	0.40	0.145	0.42	0.34	0.130	0.37
150	0.31	0.32	0.145	0.35	0.28	0.125	0.30
185	0.25	0.26	0.145	0.29	0.22	0.125	0.26
240	0.195	0.20	0.140	0.24	0.175	0.125	0.21
300	0.155	0.16	0.140	0.21	0.140	0.120	0.185
400	0.120	0.13	0.140	0.19	0.115	0.120	0.165

Note: r=conductor resistance at operating temperature

Z=impedance, x=reactance

Table C: Rating Factors for Other Ambient Air Temperatures (XLPE Insulated)

Ambient Temperature	25℃	30℃	35℃	40℃	45℃	50℃	55℃	60℃	65℃	70℃	75℃	80℃	85℃
Rating Factor	1.02	1.00	0.96	0.91	0.87	0.82	0.76	0.71	0.65	0.58	0.50	0.41	0.29

Table D: Rating Factors for Other Ground Temperatures (XLPE Insulated)

Ground Temperature	15℃	20℃	25℃	30℃	35℃	40℃	45℃	50℃
Rating Factor	1.00	0.97	0.93	0.89	0.86	0.82	0.77	0.73

Table F: Group Rating Factors for Cables Installation

Group Rating Factors			Number of Circuits
			2	3	4	5	6	7	8	9	10	11	12
1	For circuits of 2 Single core cables laid flat touching horizontal formation, laid direct in ground		0.79	0.68	0.62	0.57	0.54	0.52	0.50	0.48	0.47	0.46	0.45
2	For circuits of 3 Single core cables in trefoil touching, laid direct in ground		0.78	0.66	0.61	0.56	0.53	0.50	0.49	0.47	0.46	0.44	0.43
			Number of Cables in a Group
			2	3	4	5	6	7	8	9	10	11	12
3	For twin or multi-cores cables in horizontal formation, laid direct in ground	Spaced 0.15m	0.87	0.78	0.74	0.70	0.68	0.66	0.64	0.63	0.62	0.61	0.60
		Spaced 0.30m	0.91	0.84	0.81	0.78	0.77	0.75	0.75	0.74	0.73	0.73	0.72
			Number of Ducts in a Group
			2	3	4	5	6	7	8	9	10	11	12
4	For twin or multi-cores cables in single-way ducts horizontal formation spaced 0.30m apart		0.93	0.88	0.85	0.83	0.82	0.81	0.80	0.79	0.79	0.78	0.78

Table G Correction Factors for Groups of More than One Circuit of Single Core Cables, or More than One Multi-Cores Cable

Reference Methods of Installation		Correction Factor (Cg)
		Number of Circuits or Multi-cores Cables
		2	3	4	5	6	7	8	9	10	12	14	16	18	20
Enclosed (Method 3 or 4) or bunched and clipped direct to a non-metallic surface (Method 1)		0.80	0.70	0.65	0.60	0.57	0.54	0.52	0.50	0.48	0.45	0.43	0.41	0.39	0.38
Single layer clipped to a non-metallic surface (Method 1)	Touching	0.85	0.79	0.75	0.73	0.72	0.72	0.71	0.70	-	-	-	-	-	-
	Spaced*	0.94	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90	0.90
Single layer multi-cores on a perforated metal cable tray, vertical or horizontal(Method 11)	Touching	0.86	0.81	0.77	0.75	0.74	0.73	0.73	0.72	0.71	0.70	-	-	-	-
	Spaced*	0.91	0.89	0.88	0.87	0.87	-	-	-	-	-	-	-	-	-
Single layer single core on a perforated metal cable tray, touching (Method 11)	Horizontal	0.90	0.85	-	-	-	-	-	-	-	-	-	-	-	-
	Vertical	0.85	-	-	-	-	-	-	-	-	-	-	-	-	-
Single layer multi-cores touching on ladder supports (Method 13)		0.86	0.82	0.80	0.79	0.78	0.78	0.78	0.77	-	-	-	-	-	-

*Space means a clearance between adjacent surfaces of at least one cable diameter (De). Where the horizontal clearance between adjacent cables exceeds 2 De, no correction factor need be applied.

Note:

The factors in the table are applicable to group of cables all of one size. The value of current derived from application of the appropriate factors is the maximum continuous current to be carried by any of the cables in the group.

If, due to known operating conditions, a cable is expected to carry not more than 30% of it’s grouped rating, it may be ignored for the purpose of obtaining the rating factor for the rest of the group.
For example, a group of N loaded cables would normally require a group reduction factor of Cg applied to the tabulated It. However, if M cables in the group carry loads which are not greater than 0.3CgIt amperes, the other cables can be sized by using the group rating factor corresponding to (N-M) cables.

Factors are given for single layer of cables do not apply when cables are installed in more than one layer touching each other.

For circuits having more than one cable in parallel per phase, each set of three conductors should be considered as a circuit for the purpose of this table.