Risk based approach for surge arrester replacement

Surge arrester is a critical component in tropical countries since the likelihood to have a lightning stroke in the transmission system is higher in comparison to those in sub tropics. Therefore, assuring the reliability of this component is important. However, the surge arresters are sometimes being overlooked during the replacement plan because of its insignificant price in comparison to the protected assets. Transmission utility mostly just install and forget. This paper presents a methodology to replace the High Voltage (HV) and Extra High Voltage (EHV) surge arresters based on the risk of a failure. The condition assessment based on resistive leakage currents and the statistical reliability curve based on lifetime assessment define the likelihood of failure. While the consequences are based Safety, Extra Fuel Cost, Energy Not Served (ENS), Customer Satisfaction, Leadership, and Environmental Impact. The risk is then estimated by multiplying the likelihood of failure and consequences. It can be used to prioritise replacement, particularly when resources (budget, spares, workability) are limited.