Abstract
An increased failure of Pole Mounted Transformers (PMT) in the 11 kV Arabel Platkoppie distribution line in the Gauteng province of South Africa has been reported to be 59% between the years (2017-2021). In most reported cases, lightning activities in the Arabel Platkoppie distribution line are identified as the primary cause of PMT failure. Owing to this high probability of failure risk observed, the effectiveness of both single and double surge arrester protection technologies is analysed using the probabilistic risk evaluation technique. A simulation of the Arabel Platkoppie distribution line is performed in this quantitative study using the transient electromagnetic program (EMTP-RV_ EMTPWorks 2016a version 3.3) to evaluate the performance of both single and double surge arrester protection technologies, which is exposed to lightning strikes of between 10 kA and 120 kA at Arabel Platkoppie distribution line. The two surge arrester technologies are simulated considering the energy handling capability of each surge arrester in both proposed technologies and taking into account the overvoltage induced around the lightning strike and across the PMT.
The simulation results show that double arrester protection reduces the annual outage rate of arresters from 17.4 to 9.6 outages/year, thus improving the average life expectancy of the arrester from 5.8 to 10.4 years. The use of the double surge arrester technique is seen to improve the energy handling capability of surge arresters by 53.9%, consequently reducing the probability of PMT failure. The main objective for evaluating the risk of failure of a surge arrester connected to the overhead distribution lines was to ensure that the surge arresters offer sufficient protection to pole-mounted transformers connected to the 11 kV distribution line to enhance the performance of overhead distribution lines.