Simulation of transformer PD pulse propagation and monitoring for a 500 kVsubstation

This paper discusses the development of a simulation model to study the pro pagation of partial discharge (FD) pulses of transformers in a 500 kV subst ation. The results will be used to design an on-line PD monitoring system f or transformers. The impedance matrix of a 500 kV, single-phase transformer is computed based on geometry data and its external coupling network (ofte n referred to as coupling impedance) is calculated with electromagnetic tra nsients program (EMTP). It was found that the frequency characteristic of t he coupling network is complex and that the traditional lumped coupling cap acitance representation is only feasible at <60 kHz. The entire substation network was included to calculate the PD propagation of the transformer, PD responses are obtained at the tank grounding and 500 kV bushing tap ground ing with a simulated PD pulse injected at the 500 kV terminal and 220 kV te rminal of the transformer, respectively. Simulation shows that, using the r esonant frequency of the substation network as monitoring frequency, one ef fectively can increase the monitoring sensitivity. The off-line and online PD calibration also can be made based on the developed simulation model.