Auto Reclose Protection Scheme for Mixed Overhead Line and Underground Cable Transmission Line: A Review in PT PLN (Persero) UIT JBB

Mixed transmission lines, comprising overhead lines and underground cable lines, are utilized to facilitate electrical transmission in high-voltage infrastructure, particularly in places with specific requirements, including urban areas or locations separated by bodies of water. Given the distinct fault characteristics of each transmission type, implementing auto-reclose (AR) protection schemes is challenging. While most faults in overhead lines are transient, allowing for the activation of the auto-reclose scheme. However, underground cable faults are typically permanent, necessitating the deactivation of the auto-reclose scheme. This study explores the protective schemes applied to mixed transmission lines at PT PLN (Persero) UIT JBB. The utilization of advanced features in modern distance relays, the implementation of circulating current protection (CCP), and the installation of optical current transformers (OCT) are discussed as methods of identifying faults in mixed transmission lines. The protection scheme has been developed to discriminate between faults occurring on overhead or underground cable lines, ensuring the circuit breaker receives the appropriate trip or reclose orders. However, each mixed transmission line has different requirements to achieve a reliable and efficient protection system.