Pockels Effect Based Electro-Optic Sensor for Partial Discharge Measurement in Medium and High Voltage Equipment

The aim of the present work is to investigate the efficiency of electro-optic electric field sensor to characterize and detect the partial discharges in medium or high voltage equipment such as air or gas insulated switchgear. Partial discharges (PD) are frequently caused by an increase in the electric field surrounding conductors (metal particles, spikes, etc.) or at the level of cavities and cracks in solid insulators (cables, insulators, etc.). These phenomena cause gas ionization, heating, material physicochemical degradation, electromagnetic disturbances, and, as a result, premature aging of the insulation. Traditional measurement methods based on purely electrical techniques such as HFCT and UHF antennas allow a global measurement of partial discharges in the whole system. This work presents a study of Pockels effect based electro-optical sensors for partial discharge measurement under AC and DC voltage waveforms and compare their signals to those of traditional methods. Having no metallic parts, these sensors offer a local characterization of the discharge based on the induced local electric field variations.

I. Introduction

One crucial step in improving electrical network reliability is the ability to monitor high-voltage equipment such as switchgears, transformers, and wall bushings. Among its numerous advantages, medium voltage (MV) and high voltage (HV) air or Gas Insulated Switchgears (GIS) plays a critical role in the transmission of high-voltage electrical energy. However, during operation, GIS is susceptible to insulation degradation caused by partial discharge (PD) activities. Despite the relatively small magnitude of these PD, they have the potential to gradually deteriorate the insulation over time, eventually leading to breakdown or failure [1].