Case Study of Medium Voltage Load Break Switch Failure in Indonesia

One of load break switch (LBS) cubical had been burn in Jakarta area. This study was performed to gain a root cause of the failure based on field data and the simulation program. Historical recorded data from relay showed the occurred phenomena during the disturbance. Some hypotheses were built from that relay data. Furthermore, to ensure the hypotheses, simulation was conducted by modelling the system and considering recorded data from relay. According to the field data and simulation, it was found that the cause of the SF6 LBS failure was arcing on one of the loose contacts. Arcing lead phase to ground fault. Arcing lasted for a long time because the fire extinguisher ability of SF6 had degraded. This made the pressure in chamber rise then the explosion was occurred which caused three phases to ground fault in LBS.