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.