A cost effective solution for increasing ratings on underground transmission cables-a case study

Abstract

The capacity of four parallel 69KV pipe type cable circuits was evaluated based on measurement of load and temperature data and thermal modelling. Summer normal and emergency ratings were lower than required. The altematives considered to achieve the rating increase are discussed. Increasing the usable capacity by implementation of a dynamic real-time rating system was recommended. The dynamic rating system, installed in 1997, has provided improved ratings which so far has deferred or possibly eliminated the need for circulation equipment. 0-7803-5515-6/99/$10.00 0 1999 IEEE

Managing cable thermal stress through predictive ratings

“…Given the relatively short durations of peak loads and the comparatively long thermal time constants of high voltage cables, it is often possible to load cables beyond their continuous current rating without the cable exceeding its operating temperature limit. Many utilities are now beginning to use dynamic ratings as a method of using this additional capacity safely [1,2,3], however this data is not available at the day ahead planning stage, which would be very valuable to network operators.…”