Online monitoring of partial discharge initiated under metallic protrusion defect in high humidity by measuring air decomposition by-products

Metallic protrusion defect is one of the important hazardous defects in high voltage equipments which causes partial discharges who ultimately leads to damage and breakdown of power systems. The present experimental research is based on online monitoring of these partial discharges in high humidity (60%RH) by measuring air decomposition by-products such as Ozone and NOx gases. Needle plate experimental configuration has been used to simulate protrusion defects and study is conducted at 15mm, 20mm, 25mm and 30 mm gap distance respectively. Temperature and pressure were kept constant during all testing. The inception and steady discharge voltages were observed along with measuring Ozone and NOx gases in ppb after PD. The constant low voltage of 4 kV is applied to generate PD and maximum as well as average incremental value of air decomposition by-products are noted. Finite element analysis of protrusion defect has been done and experimental results of air by-products concentrations are matched with numerically calculated field strength. Moreover a primary mathematical relationship is developed between concentration of air by-products and electric field strength. Our results shows that air by-products concentrations increases with partial discharge in protrusion defect which leads to an indirect way for its detection and monitoring.