Cables shall only be operated at their full rating if the minimum current at which circuit protection is designed to operate does not exceed 1.5 times (in case of cables in air or in ducts) or 1.3 times (in case of cables laid direct in the ground) the values tabulated in Tables I to III.

NORMAL CONDITIONS OF INSTALLATION
1	Maximum Conductor Temperature	70°C For GPPVC Insulation and 85°C For HRPVC Insulation
2	Thermal Resistivity Of Soil	150°C cm/w
3	Thermal Resistivity Of PVC	650°C cm/w
4	Ground Temperature	30° C
5	Ambient Air Temperature	40° C
6	Depth Of Laying	75 cms

SHORT CIRCUIT RATING IN K. Amp. (For One Second Duration)
Area of conductor sq. mm.	Maximum Conductor Temperature
	G.P. PVC	H.R. PVC
1.50 sq. mm.	0.169	0.153
2.50 sq. mm.	0.283	0.255
4.00 sq. mm.	0.452	0.406
6.00 sq. mm.	0.679	0.612

FORMULA FOR CALCULATING SHORT CIRCUIT
	I1		I1 = Short Circuit Current for one seconds.
It =	---------		It = Short Circuit Current for t seconds.
	√t		t = Duration in seconds
Maximum Conductor temperature during short circuit is 160°C for both G.P. PVC & H.R. PVC Cables.

NOTE :
For cables in air no reduction in current ratings is necessary provided that:

1. The horizontal clearance between circuit is not less than six times the overall diameter of an individual cable. Not less than the overall width of individual circuit, except the horizontal clearance in any case need not exceed 150 mm.

2. The vertical clearance between circuits is not less than 150 mm.

3. If the number of circuits exceeds 4, they are installed in a horizontal plane.