Abstract
With an increasing interest in ultra-high frequency (UHF) partial discharge (PD) measurements for the continuous monitoring of power transformers, it is necessary to know where to place the UHF sensors on the tank wall. Placing a sensor in an area with many obstructions may lead to a decrease in sensitivity to the UHF signals. In this contribution, a previously validated simulation model of a three-phase 300 MVA, 420 kV power transformer is used to perform a sensitivity analysis to determine the most sensitive sensor positions on the tank wall when PD activity occurs inside the windings. A matrix of UHF sensors located on the transformer tank is used to perform the sensitivity analysis. Some of the windings are designed as layer windings, thus preventing the UHF signals from traveling through them and creating a realistic situation with very indirect propagation from source to sensor. Based on these findings, sensor configurations optimized for UHF signal sensitivity, which is also required for PD source localization, are recommended for localization purposes. Additionally, the propagation and attenuation of the UHF signals inside the windings and the tank are discussed in both oil and air.
Highlights
Since power transformers are vital components of electrical networks, their condition assessment is of utmost importance
Since ultra-high frequency (UHF) partial discharge (PD) measurement requires the placement of UHF sensors at different positions on the transformer tank [9,15,16], it is required to analyze the sensitivity of various prospective sensor positions
300 MVA, 420 kV power transformer, in which artificial PD sources were placed inside the winding, to determine the positions on the tank wall where the UHF sensors could measure PD pulses from inside the winding with the highest sensitivity
Summary
Since power transformers are vital components of electrical networks, their condition assessment is of utmost importance. In an experiment performed on a three-phase 300 MVA, 420 kV grid coupling power transformer, holes were drilled at different points on the transformer tank, and monopole antennas were installed [17] These monopole antennas were used to transmit and receive artificial UHF signals generated by a pulse generator. Since no artificial PD sources could be placed inside the windings, the propagation of the EM waves certain positions were recommended for installing UHF sensors. In this investigation, using the simulation model, multiple artificial PD sources were placed in the maximum peak-to-peak voltage received by the sensors, the most sensitive sensor positions were the windings, and an array of sensors were used to measure the signals from each source. The difference in signal propagation and attenuationSetup in two dielectric mediums (air and oil) were studied
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