Optical measurement of partial discharges under impulse voltage on ceramic substrates embedded in silicone oil

This paper presents an experimental study of Partial Discharges and light emission with ceramic substrates embedded in silicone oil, under ac and square high voltage. Two types of ceramic materials used in power electronics modules are considered: Aluminum Nitrite (AlN) and Alumina (Al₂O₃). With AlN, a large light emission due to the electroluminescence of the ceramics occurs during the negative dV/dt. This phenomenon is not observed with Al₂O₃. With Al₂O₃ and silicon oil, the light emitted is only due to PDs, and recording under square voltage wave shows that PDs are more numerous and/or more intense compared to ac. Square voltage is more relevant to actual working conditions within power electronics modules than ac.