The Smart Solution for the Prediction of Slowly Developing Electrical Faults in MV Switchgear Using Partial Discharge Measurements

An electrical fault in switchgear results in interruption of power supply, damage to equipment, and poses a hazard to personnel. This paper focuses on the detection of slowly developing faults leading to internal arc, using online monitoring technologies in medium-voltage switchgear. Unconventional radio-frequency (RF) techniques for discharge measurement are highly attractive but have not been widely applied in the industry due to their ineligibility to quantify actual discharge. On the basis of various benefits, a new application of a differential electric field (D-dot) sensor for partial-discharge (PD) measurements has been introduced in this paper. The reliability of the sensor has been confirmed through comparison with a commercial high-frequency current transformer. An attempt has been made to quantify the apparent charge of online PD measurements. The energy of signal captured by the D-dot sensor has been compared with the apparent charge quantity calculated from current pulse measured by the conventional method. A second degree polynomial relation exists between the cumulative energy and apparent charge. It has been shown that when apparent charge is plotted against the cumulative energy of the RF signal for a number of pulses, defects can be separated on the basis of cluster positions within the scatter plot.