Study Of The System For Ultrasonic Location Of Partial Discharge In Transformer

Insulation fault of electric power equipment is the prime issues of High-voltage power transmission. As one of the important equipments of the electric power network, monitoring the insulation of large power transformers is of great significance to guarantee the security and stable of the power grid. Detection and location the Transformer inner partial discharge (PD) source is a common means of monitoring the insulation, it can effectively evaluate the situation of transformer's insulation level, and provide a scientific basis for the transformer overhauling.The method for ultrasonic location of transformer PD is the development direction of the current transformer insulation detection. Its characteristic is the stronger anti-interference capability and locating conveniently and has been widely used domestic and abroad. However, in fact, due to the changing conditions, acoustic signal of the PD measurements has interferences too, on the other hand, because of the complex inner structure, the ways of propagating for PD acoustic signal could not be accurately forecasted. It makes the result of Signal extraction and fault location affected. Domestic and foreign scholars have done in-depth study on these issues and came up with a series of new theories and methods.Aiming at these problems, the main researches are as follows:(1)The study of the ultrasonic signal's propagating rules inside transformer. Design test plans to demonstrate the rules of ultrasonic on velocity, route, diffraction phenomenon.(2)The way of Combination traditional Fourier analysis and wavelet packet transform was presented to eliminate interferences basing on the characteristics of the interferences on field PD measurement. The capability of eliminating interferences by this way was analyzed by computer simulation contrasting other methods.(3 ) Coming up with an effective method to judge ultrasonic diffraction phenomenon and fix the location result of the way that thinking all the equivalent sonic velocity are the same, on the other hand, judging the reliability of the result fixed.(4)Involving in the upgrading for the Ultrasonic positioning system JFD-2A, and explaining its software, hardware, application function. Finally a field result of JFD-2A was presented.In brief, in this dissertation, basing on many field measurements and a number of laboratory tests, combination of existing theories and methods, we have had own ideas on how to eliminate interferences and locating the PD source. Furthermore we have demonstrated these ideas by laboratory tests and computer simulation, and the result show the capability of existing ultrasonic positioning system was enhanced.