MV Switchgear

Online Partial Discharge Monitoring of MV Switchgear
Condition assessment (CA) is the process of monitoring a parameter or condition indication in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintenance. The use of CA allows maintenance to be scheduled, or other actions to be taken to prevent failure and avoid its consequences.
The diagnosis of electrical equipment as decision aid tool for maintenance (postponing or advancing preventive maintenance, troubleshooting), residual life evaluation (prognosis, can we rely on equipment), actual performance evaluation (achieving optimum, increasing or reducing), forensic investigations, etc. The diagnosis integrates diagnostic tests and other available data to provide information on equipment condition or failure mode. The diagnostic methods – also referred to as condition assessment methods – include technology or techniques using tests, condition measurements and other examinations that obtain one or more condition indicators or symptoms. Sensors, acquisition systems, communication, signal processing, data analysis, software and firmware would be used in the diagnostic method. Condition indicators are quantitative or qualitative values (parameters) related to the condition of one part or one function of the switchgear.
PD measurements provide important information about the health condition of the switchgear insulation. Traditionally PD tests have been used as quality assurance measurements during the production process of the switchgear in order to check for defects in insulation that could appear during the manufacturing process. Over the last 10-20 years they also started to be used for testing equipment in the field, which will be the focus of this section.
Some of the causes of PD in HV/MV switchgear are assembly error, free moving metallic particles, metallic protrusions or sharp edges fixed on the conductors, poor or loose electrical contacts, defects in solid insulators such as voids, cracks and metallic particles on insulator surface and contamination of the insulation medium.
Since PD activity causes progressive deterioration of insulating materials, the condition of the insulation should be monitored, preferably during the lifetime of the device. Because PD can increase the risk of insulation breakdown, early detection and location are important.