Comparison of the effect of fixed metallic defects in coaxial gas insulated switchgear condition monitoring

Gas insulated switchgear assumes an indispensable equipment for high voltage transmission of electrical energy because of its focal points of high unwavering quality and execution, smaller in measurements and extraordinary compatibility with the environment. It utilizes sulphur hexafluoride gas as its insulant and coolant in view of its high dielectric quality and superb circular segment extinguishing capacity. Gas insulated switchgear in operation suffers the challenge of its insulation deterioration that leads to its failure due to the activities of partial discharge that is caused by defects. This failure is calamitous and it will prompt to whole power out stage that will affect all classes of human exercises. In order to monitor the condition of GIS, in this studies a simulated coaxial decomposition chamber was designed and used to simulate the decomposition of SF6 under the effect of fixed copper (Cu) and aluminium (Al) foil metallic artificial defect on the surface of the spacer in the chamber at the pressure of 0.2MPa when energizing with high voltage for a period of about 50 hours. The decomposition products of Cu and Al foil fixed defects detected offline by FTIR spectrometer are HF, SOF2, SOF4, SO2F2, SO2F10, SiF4, SO2, CO, C2F6, CF4 and SO2, SO2 F2, C3F8 and C2F6 respectively. These decomposed products and its concentration identify the type and the magnitude of fault in switchgear (contamination fault) and it shows that Cu fixed defect is more harmful to GIS than fixed Al foil defect.