Opto Electronic Technique for Detection of Corona Discharges in Air and Oil

A study was undertaken in the laboratory of CPRI to understand the detection capability of corona/partial discharges in air and oil medium using opto electronic technique. The experimental investigations were carried out in a high pressure test chamber fitted with high voltage bushing, electrode arrangement with a moving seal, view ports, gas inlets and outlets. PD measuring system consisted of ac high voltage test setup, fluorescent optical fiber, normal optical fiber, fiber adaptor, photomultiplier tube and picoscope for detection of discharges by optical method. Simultaneously the discharges were also detected by electrical method using the conventional system consisting of a high voltage ac source, coupling capacitor cum standard capacitive voltage divider, PD detection unit and test cell. The studies were conducted both in air & oil under uniform and non-uniform electric fields using point plane electrode geometry. The electrode gap distance is varied from 5 mm to 30 mm. The response of different colored fluorescent optical fiber was studied. The results are presented and discussed.