Through fault current monitoring system to predict the degradation of transformer withstand capability

PLN P3B Jawa Bali is a unit that responsible for managing and operating the transmission system in Jawa and Bali area. For this utility, power transformer is one of the equipments that has important role in the transmission system, therefore various efforts have been done to prevent transformer failures. To prevent unexpected transformer failure, the condition assessment of distribution transformers is done. Distribution transformer failure analysis has been done as the early stage of the assessment. The results of the analysis indicate that faults on 20 kV feeders are the main root cause of the damage on distribution transformer (150/20 kV and 70/20 kV). Some references also mentioned that the transformer failures caused by 20 kV feeder faults are highly affected by the fault currents and duration. Therefore, this paper will presents about the development of the through fault current (TFC) monitoring system to predict the degradation of transformer withstand capability and its application on distribution transformers 150/20 kV 60 MVA. This system consists of TFC logger, PC concentrator and web based database system. TFC logger will record the fault current and duration that exceed the normal current on the transformer and then send the data to the server. The cumulative TFC data will be used to predict the degradation of transformer withstand capability.