CURRENT RATINGS PVC CABLE

CURRENT RATING (PVC)

The current ratings in table 1 & 2 based on the normal conditions of installation as described below :

  • Maximum condr. temperature 70C
  • Ambient air temperature 40C
  • Ground temperature 30C
  • Depth of laying 75 cm (for cable laid directly in ground (1.1. KV)
  • Thermal resistivity of soil 150C cm/watt
  • Thermal resistivity of cable 650C cm/watt
  • Max. short-circuit conductor temperature 160C
  • Max. Ambient Air Temperature 55C

Installation method and rating factors are given in tables 1 to 6


Rating for variations in ground temperature for cables laid directly in ground and in ducts

Ground temperature C 15 20 25 30 35 40 45 50 55
Rating factor 1.17 1.12 1.06 1.0 0.94 0.87 0.79 0.70 0.60

Rating factors for variation in ambient air temperature

Air temperature C 25 30 35 40 45 50 45 55
Rating factor 1.25 1.16 1.09 1.00 0.90 0.87 0.80 0.69

Rating facors of group of twin and multicore cables laid directly in ground in horizontal formation

No of cables Rating factor for axial spacing
Touching 15 cm 30 cm 45 cm 60 cm
2 cables 0.78 0.81 0.85 0.88 0.90
3 cables 0.68 0.71 0.77 0.81 0.83
4 cables 0.61 0.65 0.72 0.76 0.79
6 cables 0.53 0.58 0.66 0.71 0.76
8 cables 0.48 0.54 0.62 0.67 0.72

Rating factors of groups of twin and multicore cables laid directly in ground in tier formation

No of cables Rating factor for axial spacing
Touching 15 cm 30 cm 45 cm 60 cm
4 cables 0.60 0.67 0.73 0.76 0.78
6 cables 0.51 0.57 0.63 0.67 0.69
8 cables 0.45 0.51 0.57 0.59 0.61

Rating factors for variation in depth of laying in ground

Depth of laying (cms) 75 90 105 120 150 150 & above
Rating factor upto 25 sq. mm. 1.00 0.99 0.98 0.97 0.96 0.95

Group-rating factors for cables installed in ground, seperated by more than 7 cms.

No. of cables 1 2 3 4 5 6
Single core D.C. cables & multicore power cables 1.0 0.90 0.80 0.75 0.70 0.65
Single core A.C. cables 1.0 0.80 0.75 0.70 0.65 0.60