Comprehensive Analysis of Lightning-Induced Faults and SOTF Protection Malfunctions in 220 kV Transmission Lines: Case Study of Chaglla Hydroelectric Plant

Sanchez A.M.; Yuan X.; Alvarez W. · 2025 25th Conference of the Electric Power Supply Industry, CEPSI 2025 (2025) · DOI: 10.1109/cepsi66359.2025.11403435

Resumen

Lightning strikes frequently cause costly outages and threaten the stability of high-voltage transmission systems. This paper details a significant power disruption at Peru's Chaglla hydroelectric plant (450 MW), where lightning strikes on its 220 kV transmission lines (L-2150/2151) triggered a cascade of events culminating in the malfunction of the Switch On to Fault (SOTF) protection system. A detailed analysis reveals that a faulty Power Swing Block (PSB) function inadequately inhibited distance protection (function 21), leading to unintended SOTF activation. This resulted in a loss of synchronism, severe grid oscillations, and the activation of frequency drop protection, causing a substantial power outage. Empresa de Generación Huallaga S.A. (EGH) implemented comprehensive corrective actions, including modifications to the PSB function, enhancements to the protection schemes, and the strategic installation of lightning arresters. These improvements significantly enhanced grid reliability and resilience. This case study offers valuable insights and practical solutions for mitigating atmospheric disturbances in large-scale power systems, highlighting the crucial interplay between lightning protection, power swing dynamics, and protection system coordination. Some simulations and test supported the effectiveness of the implemented solutions. The results demonstrate the importance of proactive system upgrades and robust protection strategies to ensure the secure and reliable operation of high-voltage transmission networks.