The research was carried out on Sempidi feeder in Kapal area electric power house to analyze influence of using the ground wire to lightning surge interference at 20 kV SUTM distribution system. Based on the research is showed that amount of interference in Sempidi feeder because lightning attack before and after using ground wire, have interference decrement as 85,71%, and also decrement of turned off time duration as 38 minutes 34 seconds. And using genetics algorithm to determine protection angle at SUTM is used 41° and 29°. That\u27s mean the angle has been matched with the toleration of protection angle. From those results, it needs to using protection to lightning surge such as a ground wire
