A New Method to Detect the Inter-Turn Short Circuit Fault of Dry-Type Air-Core Shunt Reactor

Due to the insulation fails caused by complex factors, such as the manufacture factors, transportation and complicated working environment, inter-turn short circuit fault is one of the frequent failures of shunt reactor, at the early stage of whom, its current is not high enough to trigger the protection equipment. However, the current in the shorted turn is very high, which causes serious copper loss, resulting in high temperature rise. In severe case, it will cause fire accident and explosion. Thus, it’s important to design a sensitive and reliable method to detect the inter-turn short circuit fault at its early stage. In this paper, a method based on the power loss factor (PLF) considering both the activate power and equivalent resistance of reactor, is proposed to detect the inter-turn short circuit fault of an air-core shunt reactor considering the effect of insulation resistance. Taking a BKDCL−20000/35 dry-type air-core shunt reactor as an example, the inter-turn short circuit faults occur at different axial heights and coil layers are investigated. The electrical parameters, including equivalent resistance, equivalent inductance, active power, reactive power etc. are presented and comparison is implemented between the normal condition and failure conditions. The current and active power of the shorted turn is calculated and analyzed, which are used to explain the parameters variation of the reactor when inter-turn short circuit fault occurs. Finally, PLF under various working conditions is computed and presented, which provide an alternative to monitor the inter-turn short circuit fault.