Partial Discharges testing in MV switchboards: sensitivity evaluation of embedded sensors

The performance of a new idea of sensor for detecting partial discharge in switchboards is developed in this paper. A capacitive divider embedded in switchboard bushing is tested using two types of voltage impulse sources, that is, a calibrator and an object generating internal partial discharges (the latter is chosen based on the consideration that partial discharges from internal cavities are the most harmful phenomenon affecting insulation life). It is shown that the sensor embedded in a switchboard bushing has very good sensitivity to defects located inside the switchboard and also at the switchboard cable terminal, and much less sensitivity, compared to a HFCT, to disturbances coming from the electrical circuit connected to the switchboard. This would favor both partial discharge identification and their location, enabling effective diagnosis and alerting.