LAUSR

Surge arresters are usually used to protect distribution feeders against randomly distributed lightning overvoltages. However, there is a probability of surge arrester failure due to an increase in its absorbed energy over the withstand capability. This paper experimentally and theoretically evaluates the application of a compound overvoltage protection scheme to avoid this failure. The compound overvoltage protection consists of an installed spark gap in parallel with an existing surge arrester to limit the risk of surge arrester failure. The experimental evaluation is performed by applying standard lightning impulse voltage waveform, 1.2/ $50~\mu \text{s}$ according to IEC Standard 60060-1. The evaluation is carried out without and with sparkgap adjusted at different lengths. The energy stress of the surge arrester with and without sparkgap is theoretically carried out using the ATP/EMTP software considering an overhead distribution feeder. The statistical evaluation for the failure risk assessment is performed using the MATLAB software. The results indicate that the installation of the spark gap in parallel with the surge arrester relieves the thermal stress on the surge arrester, and thus eliminates any risk of surge arrester failure using the proposed coordination.