Comparing IEC60270 and RF partial discharge patterns

Defect classification using partial discharge (PD) measurement has historically been achieved by representing the data in phase-resolved form. This paper presents phase-resolved PD patterns obtained using radio frequency (RF) and conventional IEC60270 techniques for a number of different defects including free particles, protrusions, floating electrodes and voids. Oil, SF 6 and resin were used as insulating media. Each PD geometry was placed inside an aluminium test chamber fitted with an internal UHF antenna. Around 2000 RF and IEC PD pulses have been recorded simultaneously along with their phase position for each PD source configuration using a 3 GHz digital oscilloscope. Results indicate that due to the responses of each system, clear differences exist in the phase-resolved patterns, implying that more accurate defect classification should be achieved if a system is trained exclusively using either IEC or RF data. In other words, if a classification algorithm has been trained using measurements from a conventional IEC system, the accuracy of diagnosis will be reduced if RF sensors are then used to measure on-line data without re-training the system.