Protection System Failure on 150kV Transmission Line in Java-Bali Grid due to Fault Current Residual

Reliability of measurement apparatus is an important thing in order to secure the continuous supply of power in the system. Measurement error potentially affects the protection system performance. In the study, an example of protection system failure due to measurement error on current transformer (CT) on one of the 150kV transmission line in Java-Bali grid will be discussed. The failure occurs due to residual fault current that remain flow at the faulted phase even though fault clearing has been done by the primary protection of the transmission line. Therefore, the study will determine the cause of fault residual current measured by CT after fault clearing by performing simulation in application of transient analysis. In this study, the data during single phase to ground fault on the transmission line are presented. Along with the explanation of literature study related to measurement error on CT. After that, simulations using variation of CT measurement condition are performed.