Reconfiguration of Protection System on 70kV Transmission Network

This paper presents our study on the impact of changing the transformer neutral point of the grounding system from NGR 200 ohms to solid grounding on the transmission line protection system. This study was aimed to increase the sensitivity, fault clearance and delay time of the protection system. We discusses the setting of a distance relay on 2-buses 70 kV typical transmission lines in Indonesia. We conducted simulation using Matlab/Simulink software with a scenario of a single line to ground fault with difference location of faults. Based on our simulation results, the impedance of distance relay for Zone 1 is 2.2975 ohms, Zone 2 is 3.604 ohms, and Zone 3 is 4.71063 ohms. We changed the relay setting to prove that the fault fall in the correct zone so that the protection system work well.