Underground Distribution Thermal Tests in the Phoenix Area

This paper summarizes the results of an 18-month thermal test program conducted jointly by the Arizona Public Service Company and the General Electric Company to investigate thermal characteristics of soil and performance of underground equipment in the Phoenix area. The results presented include earth ambient temperatures at various depths over an annual cycle, earth thermal resistivity measurements by steady-state and transient methods, performance of direct burial and vault installation of capacitors, performance of a directly buried, 25-kVA, pole-type distribution transformer, and temperature rise of simulated cables.