A utility´s approach to the application of scout arresters for overvoltage protection of underground distribution circuits

Virginia Power (VP) experienced high failure rates on primary underground cable on their 34.5 kV distribution system in the late 1980s and early 1990s. The majority of this cable was 260 mil XLPE 1/0 aluminum unjacketed. VP has since changed to 345 mil XLPE jacketed cable in addition to the use of internal arresters in all new single phase padmounted transformers. However, there still remains a considerable amount of the older cable that is failing at an unacceptable rate. Retrofitting existing transformers with internal arresters was determined to not be economically feasible. The authors describe how, therefore, several cable protection techniques were considered in an effort to reduce transient voltages on the underground cable, including retrofitting with scout arresters. Also, digital simulations were performed to analyze the performance of scout arrester installations