Investigating Partial Discharge Characteristics in Silicone Gel for (U)WBG Power Modules Under Negative DC Voltage: A Comparative Study of Optical and Electrical Detection Methods

This paper aims to investigate the accuracy of the optical partial discharge (PD) detection technique in recording PD activity within silicone gel (SG), using conventional electrical techniques as a reference. Given the inevitable high-frequency, high-slew rate square voltage operation of (U)WBG power modules, alternative PD measurement techniques are needed to replace conventional electrical methods. Before implementing optical detection for high-slew rate square pulses, its accuracy under DC voltage conditions-where electrical PD detection is reliable due to its immunity to EMI and disturbances-must be assessed. This study analyzes PD activity within SG using a needle-to-plate electrode configuration under varying negative DC voltages, employing both optical and electrical PD detection techniques. It also examines the impact of decreasing the distance between the electrodes and compares PD signal results at various voltages between the APD optical sensor and the Omicron MPD800 software. As no previous research has correlated electrical and optical PD detection methods, this paper serves as a valuable reference for future studies involving PD measurement in encapsulation materials under high-frequency, high-slew rate square wave voltages.