Research Papers - Department of Electrical and Electronic Engineering
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Publication Embargo A measurements-based discharge location algorithm for plain disc winding power transformers(IEEE, 2005-06-20) Wang, Z. D; Hettiwatte, S. N; Crossley, P. AA measurements-based electrical method for locating partial discharges (PD) in transformers is described in the paper. This location method relies on the series resonance frequencies of the signals produced at the transformer terminals by a discharge on the winding. Based on the equivalent circuit of plain disc type winding which consists of series inductance (L), series capacitance (K) and shunt capacitance to earth (C) of the winding, an analytical location algorithm is derived which gives the relationship between the location of a discharge and its terminal response's series resonance frequencies. LKC parameters of the equivalent circuit can be estimated using the series resonance frequencies of a calibration signal measured at the bushing tap during PD calibration. The PD location algorithm was tested on 11 kV transformer winding using signals produced by a discharge simulator and real discharges, and the results confirm its validity with a location accuracy of better than 10% of the winding length. However, blind area where this location algorithm is not applicable does exist near the neutral of the winding and far away from the measuring terminal. Since this location algorithm uses the series resonance frequencies below 500 kHz, it can be implemented with conventional PD measuring circuitry and instruments to detect and locate discharges in power transformers.Publication Embargo Simulation of a transformer winding for partial discharge propagation studies(IEEE, 2002-01-27) Hettiwatte, S. N; Crossley, P. A; Wang, Z. D; Darwin, A; Edwards, GA simulation model of a continuous disc type 6.6 kV transformer winding was used to study the propagation behaviour of partial discharge (PD) pulses. The model based on multi-conductor transmission line theory uses a single turn as a circuit element with the capacitance, inductance, and losses calculated as distributed parameters. Transfer functions that describe how the location of the PD source affects the current signals measured at the terminals of the winding were calculated. The paper shows how the position of the zeros in the frequency response of the measured current signals can be used to locate the source of the discharge. Sensitivity studies on the parameters of the model were used to investigate the effect of inaccuracies in the model on the position of the zeros and hence the location of the discharge.