An Assessment of Failure Rate of Pole-Mounted Transformers Using Probabilistic Risk Evaluation of Lightning Arresters

In this study, the probabilistic risk evaluation of surge arresters is conducted in order to assess protection effectiveness of PMTs against lightning strikes. An 11 kV distribution line located in Arabel Platkoppie − a district area in Johannes-burg, South Africa − which experienced 59% of PMT failure due to lightning between 2017 and 2019, is used as a case-study. Statistical data related to lightning activities around the Arabel Platkoppie area were souced from FALLS. EMTP-RV Simulation results of direct effect of lightning strikes were used. The risk evaluation of lightning arrester, committed to the protection of PMTs, is then assessed using probabilistic failure evaluation. Resuts show that with the frequency of lightning activity recorded in the Arabel Platkoppie area, the annual outage rate is estimated to be 0.1694 outage/100 km/year, which translates to the expected average surge arrester life of 5.8 years.