Analisis Proteksi Gangguan Petir pada Transmisi 150 kV Segmen Penghantar Sei Rotan - Tebing PT PLN (Persero) UPT Medan

Abstract

Analysis Protection of Lightning Interference on 150 kV Transmission Line Conductor Segment Sei Rotan – Tebing, PT PLN (Persero) UPT Medan is motivated by a lightning interference that previously struck transmission tower 24, resulting in a peak current of 18 kA and a minimum current of 20 kA. The strike caused a flashover on the arching horn of the insulator, leading to an S-N phase fault. Based on the fault recording data from tower 24, it was found that the main issue in this study is the tower’s history of lightning-induced disturbances. The geographical location of tower 24 within an industrial area is also identified as a contributing factor, as pollutants generated from the industrial environment affect the tower’s performance. This study aims to analyze the problem-solving approach related to the frequency of lightning strikes that result in single-phase-to-ground short-circuit faults. The analysis methods used include brainstorming, fishbone diagrams, and Pareto diagrams. The brainstorming analysis indicated that both the electrical lifetime and the grounding system resistance exceeded the SPLN standard of 5 ohms. The fishbone diagram analysis further revealed that the main issue was the grounding system resistance, which measured 7.8 ohms—above the SPLN standard—preventing the lightning surge current from being fully discharged into the ground. Additionally, a gradual decline in insulation resistance due to weathering or climatic conditions was identified. According to the Pareto diagram analysis, the disturbances occurring at tower 24 of the 150 kV Sei Rotan – Tebing transmission line were caused by lightning strikes (43%), grounding system issues (11%), and insulation degradation due to the tower’s 41-year lifespan (56.94%). Another contributing factor was the insufficient protective angle against short-circuit disturbances. The required protection angles were 27.1° for the minimum current and 25.1° for the maximum current. The wave reflection analysis showed that 92.8% of the voltage was reflected, while 7.2% was transmitted. A comprehensive understanding of these issues is crucial for developing more efficient maintenance strategies and enhancing the reliability of the electrical system.