Inter-Turn Short-Circuit Detection Through Differential Admittance Monitoring in Transformers

Detecting inter-turn short-circuits in power transformers at an early stage is essential to reduce repair costs and interruption times of the electrical distribution service. Differential protection relays are widely used in this type of machine to detect faults of this nature. However, they are not effective enough when the faults are in an incipient stage where only a few inter-turns are involved. Therefore, it is of interest to develop strategies that allow early detection of this type of faults. In this work, a strategy for inter-turn short-circuit detection through differential admittance monitoring is proposed. Through computational simulations on a 5 kVA transformer, it is shown that the strategy is sensitive to faults involving from 2% of the winding with a current in the fault loop of 1 p.u. Furthermore, the fault detection strategy is not sensitive to transformer load state, load or voltage unbalance, under or over voltages, and harmonic content.