Partial discharge (PD) detection on medium voltage switchgears using non-invasive sensing methods

Like in any high voltage asset, knowledge about the presence of partial discharge in the insulation system can provide vital information about the health condition of HV apparatuses. For switchgears, a traditional PD measurement according to IEC 60270 requires the disconnection of power cables from the switchgear, and the setup of a test circuit at the terminals of it. This includes the shutdown of the switchgear and the connected cable, and comes together with downtime and manual labor on the connectors, which by itself can result in the generation of partial discharge due to mechanical stresses or improper reassembly. This can be avoided by using non-invasive PD detection principles on switchgears, which allow the detection of PD without disconnecting the cables from the switchgear, with a measurement that is performed on-line. By using different possibilities of permanent installed line couplers, VHF, UHF and acoustic sensors the results are different to IEC 60270 measurement (like during the factory acceptance test). The common available non-invasive methods are compared to the IEC 60270 -measurement in the laboratory, whereby only single and defined failures are applied to the switchgear.