On-site investigations of gas insulated substations using ion mobility spectrometry for remote sensing of SF6 decomposition

Although gas insulated switchgear and substations (GIS) belong to the most reliable components of electric power networks, failures still occur in their long term operation. A monitoring system for GIS and SF ₆-filled circuit breakers is realised on the basis of continuous sensing of the insulating gas using ion mobility spectrometers (IMS). Especially, partial discharge IMS provides power utilities a diagnostic tool able to perform on-site monitoring and event controlled inspections of the SF₆ gas. The results of on-site monitoring and on-line analyse of SF₆ contained in a circuit breaker of the hydroelectric power plant Itaipu Binacional, Brazil, before and after operation are described. Conclusions of investigations of the actual state of 36 different circuit breakers executed under service in a substation of Itaipu are presented. Finally, the structure of a system for automatic on-site sensing of SF₆-decomposition in the hydroelectric power plant of Foz do Areia, State of Parana Brazil, is discussed