Emergency-Temperature Testing on MV Jacketed Reduced-Wall TRXLPE Aluminum Cable Systems in Duct Bank

Two MV reduced-wall TRXLPE-insulated 500-kcmil aluminum-conductor cables with encapsulated XLPE jacket were designed as replacements for the 350-kcmil copper-conductor cables with bare concentric neutral. The objective was to realize substantial cost savings on the purchase of the expensive copper-conductor cables. However, it would require an appropriate reduction of the insulation thickness of the aluminum cables in order to have the same ampacity as well as to fit into the existing 90-mm (3½″) PVC conduit. An emergency temperature test to be carried out in a duct bank containing 90° bends was chosen to evaluate the overall performance of the new cable systems. Thermal, mechanical, and electrical measurements were made in the testing. The test results were compared to those obtained previously on the 350-kcmil copper-conductor cables.