National Cables - Rating Factors

National Cable manufactures and market heavy duty rugged Industrial and House Wiring Cables 250/440 Volts and 660/1100 Volts grade, 70 degree Celsius Temperature grade in (a) Single Core Unsheathed, Single Core Sheathed, Flat Twin, Flat Three Core Cables with or without ECC confirming to BS 2004/BS 6004 with Solid/ Strained Copper Conductor.

Rating Factors for Variation in Ground Temperature

Ground Temperature degree C	15	20	25	30	35	40	45
Rating Factors	1.17	1.12	1.06	1.00	0.94	0.87	0.79
Rating Factors for Variation in Ambient Air Temperature
Air Temperature degree C	25	30	35	40	45
Rating Factors	1.25	1.16	1.09	1.00	0.90
Rating Factors for groups of twin and Multicore Cables Laid in Group in Horizontal Formation
NO. Of Cables	Rating Factors for Axial Spacing
	Touching	15cm	30cm	45cm	60cm
2 cables	0.79	0.82	0.87	0.90	0.91
3 cables	0.69	0.75	0.79	0.83	0.86
4 cables	0.62	0.69	0.74	0.79	0.82
6 cables	0.54	0.61	0.69	0.75	0.78
8 cables	0.50	0.57	0.66	0.72	0.76
Group Rating Factors For Circuits of two single core Cables, Side by Side Touching, Horizontal Variation, Laid Direct in Ground
NO. Of Circuits	Spacing (between Centers of Circuits)
	Touching	15cm	30cm	45cm	60cm
2	0.79	0.86	0.91	0.93	0.95
3	0.69	0.78	0.84	0.88	0.91
4	0.64	0.73	0.81	0.86	0.88
6	0.56	0.67	0.77	0.83	0.87
8	0.51	0.65	0.75	0.82	0.86
Group Rating Factors for Circuits of three Signal Core Cables, Side by Side Touching, Horizontal Formation, Laid Direct IN Ground
NO. Of Circuits	Spacing (between Centers of Circuits)
	Touching	15cm	30cm	45cm	60cm
2	0.78	0.81	0.85	0.88	0.90
3	0.68	0.71	0.77	0.76	0.79
4	0.61	0.65	0.72	0.76	0.79
6	0.53	0.58	0.60	0.71	0.76
8	0.48	0.54	0.62	0.67	0.72
Rating Factors for Variation in Depth Of Laying In Ground
Voltage	Depth of Laying(cms)	75	90	105	120	150	180 & above
	Rating Factor upto 12sq.mm	1.00	0.99	0.98	0.97	0.96	0.95
1.1 Kv	Rating Factor upto 12sq.mm & upto 300 sq.mm	1.00	0.98	0.97	0.96	0.94	0.93