Diagnostic Methods for Gas-Insulated Substations

Various diagnostic methods of GIS have been studied and some of them were applied in the field. In this paper the principles of methods such as mechanical, chemical, electrical detection, and others are described. As mechanical methods, a highly sensitive piezo-electric acceleration sensor and an ultrasonic-wave sensor are used to detect mechanical vibration or elastic waves generated at partial discharges or ground faults. As a chemical method, the gas analysis of decomposed SF6 gas is applied to detect partial discharges or local heating . As electrical methods, external electrode, inner electrode, and magnetic coupling method, and the measurement of the GIS sheath potential are applied to detect partial discharges. As other methods, the diagnosis of internal conditions in a tank by an X-ray photograph, the diagnosis of mechanical driving systems, and the detection of local heating by an infrared camera are also described.