In order to ensure the safe operation of electrical equipment

safety of personnel as well as minimum environment pollution

it is essential to detect SF

6

leakage as earlier as possible and deal with it in time. However

there are defects in the present single sensor based system

i.e. the accuracy of detection cannot be ensured over long term. To address the problem

a distributed on-line monitoring system for detecting SF

6

leakage based on the fusion of infrared and ultrasonic dual sensor configuration has been

proposed. The basic principle is to take advantage of the infrared and ultrasonic technologies to measure the concentration of SF

6

. The infrared and ultrasonic sensors operate in an intermittent and continuous modes

respectively. This monitoring system can also measure the concentration of O

2

as well as temperature and humidity in real time. Results show that the modified ultrasonic technology simplifies the hardware and reduces the phase drift. When the ultrasonic method is applied to measuring the concentration of SF

6

the measurement accuracy is affected by the phase shift of the two signals

time difference

temperature and the length of the air chamber. According to field measurement results

the system proposed in the present work has higher accuracy and more reliability. It can be used for early detection of SF

6

leakage and timely processing of the leakages.