Transformer Model for TRV at Transformer Limited Fault Current Interruption

This chapter deals with the transient recovery voltage (TRV) of the transformer limited fault (TLF) current interrupting condition using capacitor current injection. The current generated by a discharging capacitor is injected to the transformer, and it is interrupted at its zero point by a diode. A transformer model for the TLF condition is constructed from leakage impedance and a stray capacitance with an ideal transformer in an EMTP computation. By using the frequency response analysis (FRA) measurement, the transformer constants are evaluated in high-frequency regions. The FRA measurement graphs show that the inductance value of the test transformer gradually decreases as the frequency increases. Based on this fact, a frequency-dependent transformer model is constructed. The frequency response of the model gives good agreement with the measured values. The experimental TRV and simulation results using the frequency-dependent transformer model are described.