RATING OF CABLES ON RISER POLES, IN TRAYS, IN TUNNELS AND SHAFTS - A REVIEW

This paper reviews rating of cables installed in air. The following ca ble installations are investigated (1) cables on riser poles, (2) cabl es in open and closed trays, (3) cables wrapped in fire protection cov ers, (4) cables in horizontal tunnels, and (5) cables in vertical shaf ts. The rating of cables in these installations is computed by solving energy balance equations for the unknown surface temperature with a g iven conductor current. In ampacity computations the conductor current is adjusted iteratively until permissible cable conductor and surface temperatures are achieved. It is shown in the paper how the same ener gy balance equations can be used to compute the ratings of all the abo ve cable installations.