Infrared thermography of negative DC and negatively enhanced AC point-to-plane corona discharge in air

Corona discharge for point-to-plane gaps in air was investigated with emphasis given to thermographic analysis of the air gap using an infrared scanning system. Corona discharge was generated under two conditions: using negative voltage on the point and a grounded plane, and using 60 Hz AC voltage on the point and positive DC voltage on the plane (negative enhancement of AC corona). Changes in the infrared images of the air gap were observed as the corona discharge current increased. These images showed the region of the gap with the elevated apparent temperature indicating a source of infrared radiation in the gap. The relationship between the pattern in the air gap and corona discharge current was studied. It was observed that the intensity of the infrared signal generated in the gap increased with the discharge current. Temperature distribution on the anode surface was measured. In the case of the negatively enhanced AC corona, fluctuation of the region with elevated apparent temperature was observed