Partial discharge detection by TEV sensors and signal propagation analysis in transformer model

Summary

This paper deals with a detailed study on partial discharge (PD) generated in transformers using transient earth voltage (TEV) detection method. Experiment and numerical analysis are carried out using an iron box model which simulates a tank of an actual transformer. In the test model, propagation properties of TEV signal caused by PD occurring inside and outside of the transformer model are examined. Results reveal that the electromagnetic waves generated by PD in the model can leak from the opening window, having special frequency determined by the size of the opening window. It is also found that TEV sensor placed on the surface of the tank detects a TEV signal originating from the leaked electromagnetic wave. On the other hand, TEV signal by electromagnetic waves generated by an external PD source is found to have a wider frequency band than that by leaked electromagnetic wave. In addition, electromagnetic field and surface current analysis are performed using finite difference time domain (FDTD) method and simulated results are compared with experimental ones. As a result, it is shown that leaked electromagnetic wave excites a surface current on the outer tank wall of the transformer model. It is also found that there exists difference in the time required for TEV signal to arrive at the inside and outside sensors. The results indicate that PD emitting electromagnetic waves leaked from the dielectric discontinuities can be detected by the TEV method. Furthermore, these results suggest a combination of the detected waveform and its frequency band could lead to highly reliable diagnosis of the apparatus by TEV detection method.

Additional informations

Authors

Vilar Pablo Bezerra, Nobrega Luiz , Lira George Rossany Soares, Maia Marcelo