Investigating reflections and refractions effects in the UHF Location of partial discharges in power transformers using time domain simulation

The measurement of Ultra High Frequency (UHF) electromagnetic waves originated from a partial discharge (PD) source has been used for the identification and location of defects in power transformers. This method is based on the time-difference-of-arrival (TDOA) of the PD electromagnetic radiation using UHF sensors installed on the transformer. Then, it is possible to estimate the original position of the measured signals. However, it is known that the propagation of electromagnetic waves is affected by the reflections and refractions that occur inside the transformer, causing delays in propagation time and generating errors in the localization algorithms. For this reason, the refractions and reflections of the PD radiation on power transformers was studied in order to evaluate their effects on the delay of the signals arrival time. For this, the CST Microwave was used to simulate a power transformer model and to evaluate the effects of the core and windings in the wave propagation. Finally, the PD source was located from the measured signals and the error in the original source location was evaluated.