On predicting the life of polyethylene spacer-cable eroded by surface discharges in wet weather

As part of a study to evaluate the feasibility of uprating existing 15 kV spacer-cable systems to 34.5 kV, a method was developed for predicting the life of the polyethylene cable which may be eroded by electrical surface discharges in wet weather. The prediction method considers the changes in spacer surface resistance and the resulting electrical stress on the polyethylene throughout a typical year of varied surface conductivity during rain and fog, together with a measure of the quantity (Q) of surface discharges per power frequency cycle, which is related to the electrical stress. It is believed that the measurements and procedure outlined form a reasonable basis for predicting polyethylene spacer-cable life in wet weather, and for large value surface discharges the life appears to be inversely proportional to the initial Q².