A comparison of the heat dissipation performance of twin wall HDPE and earthenware cable ducts

This paper presents the results of an extensive experimental programme conducted to investigate the heat dissipation characteristics of twin wall HDPE (high density polyethylene) cable duct. The results are compared with those for more traditional material ducts. The perceptions of some UK cable engineers are that cables installed in twin wall HDPE ducts should be de-rated by an extra 10% because of the insulating effect of the void between the twin walls. Within the paper there is a brief description of the experimental methodology used to simulate steady state conditions for cables installed in ducts. The analysis of the results reveals that there are only small differences in the heat dissipation characteristics between twin wall HDPE and clayware duct cable ratings are thus affected by only a minimal amount. The results also offer cable engineers more information on the prediction of temperatures in and around cables installed in ducts. It is hoped that the information presented will reduce the number of over-sized cables in operation, and hence reduce initial costs.