Advanced monitoring system for gas density of GIS

Detection of SF₆ gas leakage from a gas insulated switchgear (GIS) has recently become an important issue from an environmental standpoint in addition to the demands for the insulating reliability. This paper describes a state-of-the-art gas leakage detection system, which consists of a high-performance gas pressure sensor and a new algorithm improving accuracy of the leakage rate calculation. The gas pressure sensor has enough properties, resolution of 20 Pa and the stability of 0.004 % per year. Furthermore, in order to achieve high accuracy of leakage detection in the actual field, the new algorithm of the leakage rate calculation has been developed to cancel the interference due to solar radiation and weather. A yearlong test of the 84 kV GIS system demonstrated that the algorithm reduces fluctuations of obtained gas pressure to one fifth and enables to detect the leakage of 0.5 % per year, which is standardized maximum leakage by the new standard, IEC 62271-203.