Optimization of the 20 kV Protection System to Reduce the Number of Affected Customers and Improve Distribution Network Reliability at PT PLN (Persero) ULP Kisaran

Abstract

The reliability of the electric power distribution system is a critical aspect in ensuring the continuity of energy supply to customers. One factor affecting reliability is suboptimal coordination of the protection system, which can lead to widespread outages due to non-selective relay operation. This study aims to optimize the protection relay settings in the 20 kV distribution system at the Kisaran Substation of PT PLN (Persero) ULP Kisaran to reduce the number of customers affected by outages and improve grid reliability. The research methodology involved analyzing existing conditions, calculating short-circuit currents, evaluating relay coordination, and optimizing the parameters of the Overcurrent Relay (OCR) and Ground Fault Relay (GFR) based on inverse characteristics in accordance with IEC standards. The optimization results show that the OCR pickup value on Feeder KN.04 was successfully reduced from 600 A to 310 A, while on Feeder KN.06 it was reduced from 600 A to 253 A. The OCR Time Multiplier Setting (TMS) was adjusted to 0.16 on KN.04 and 0.17 on KN.06, while the GFR TMS was increased from 0.15 to 0.45 on both feeder lines to achieve more selective protection coordination. Simulation results show that the optimized settings improve the sensitivity and selectivity of the relays, resulting in faster and more precise fault isolation. These improvements in protection coordination result in a reduction in the outage area and the number of affected customers, which in turn improves the System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI) in the 20 kV distribution system at the Kisaran Substation.