Partial Discharge Detection under Impulse Voltage Application by Acoustic Emission Sensors in Oil/Pressboard Composite Insulation System

Summary

Power transformers use an oil and pressboard composite system. In order to improve the dielectric performance or downsize the apparatus, it is essential to sophisticate partial discharge (PD) detection methods as well as to clarify PD characteristics under impulse voltage application. Various kinds of PD detection method have been proposed and developed by many researchers over a long period. For example, ultra high frequency (UHF) electromagnetic waves induced by PD are often used for PD detection, due to their high sensitivity. However, most of these researches were conducted for PD detection under AC voltage application or monitoring the condition of the apparatus and it is quite difficult to detect in the case of an impulse voltage withstand test on an actual power transformer, because of the severe electromagnetic noise emitted from sphere gap discharges in an impulse voltage generator. In this research, the authors adopted acoustic emission (AE) sensors for the purpose of separating PD signals from the electromagnetic noises by using the difference in the arrival time to the sensor between electromagnetic waves and AE signals. As a result, we clarified that PD signals were successfully detected by AE sensors after the attenuation of electromagnetic noises from an impulse generator with a reasonable time delay, which could be estimated from the distance between the PD inception spot and the AE sensor and also the velocity of the AE signals in the insulating oil.

Additional informations

Authors

Stanek Marcin, Tang , Großmann Steffen, Yi Yong, Wang Yuanjiu