| GIS (Gas-insulated metal enclosed Switchgear) is widely used in power system, and solved many problems which traditional power plants can’t. However it’s hard to detect GIS failures, which brought troubles for normal running of GIS. So how to detect GIS failures quickly and efficiently has become the most concerned problem now. This paper has designed a Ultrasonic-electric detection system to detect and locate PD in GIS.First a GIS PD simulation and test platform is established. Three typical kinds of PD signals in GIS are studied, include the fixed particles, the free particles and floating shield. With analyzing the ultrasonic and electric signal of these three faults, in the frequency domain, ultrasonic signal is mainly found to be in the range of0-25kHz and50kHz-75kHz, electric signal is found mainly to be in the range of0-40MHz. with higher energy. Then appropriate bandwidth sensors has be designed and filter parameters has be designed to improve the detection system signal-to-noise ratio by these energy distributions. This Ultrasonic-electric detection system includes ultrasonic detection system and electric detection system. Ultrasonic detection system utilizes resonance ultrasonic sensor whose central frequency is40kHz and a voltage preamplifier to detect the ultrasonic signal. Electric detection system utilizes the Rogowski coils whose frequency band is23MHz or40MHz with a voltage preamplifier to detect the pulse current signal. Then two signals are transfered to the compute by the acquisition card, which processing by our software. The software has a band-pass filter which can change parameters.Base on the Ultrasonic-electric detection system, the principal and method of faults location are studied for GIS. Then Ultrasonic-electric detection system is applied to the fault loaction on GIS PD location platform.Ultrasonic-electric detection system can detect the straight line distance by the delay of ultrasonic signal between ultrasonic sensor and PD source. But taking into account the coaxial structure of GIS, this thesis puts forward a special method. Use of the detected signal as a benchmark by Rogowski coil, this method is to compare the signal delay of two ultrasonic sensors to get the location of PD source. Compared with traditional location by single type of sensor, this system can locate the PD source easier. combined the sensitivity of electric detection with the anti-electromagnetic interence of ultrasonic detection, improve the ability of GIS PD detection. |
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