Development of on-line concentration monitoring device for SF₆ decomposition product in high voltage SF₆ switchgear

The concentration of gaseous decomposition products in SF₆ circuit breakers serves as a criterion for the internal discharge modes and discharge energy. To achieve online monitoring of the operational state of SF₆ circuit breakers through SF₆ decomposition products, a carbon nanotube sensor based on ionization principle and a detection system for micro-ampere level output current from the sensor have been developed in the present work. Based on the detection results of SOF₂ concentration it can be shown that the output current from the sensor has a monotonic relationship with the concentration of SOF₂. The detection system is able to detect the micro-ampere current output from the sensor with relatively high accuracy. The detection system can thus be used to monitor the concentration of SOF₂ in real time and be further used to study the internal discharge in circuit breakers and realize online monitoring of SF₆ decomposition products.