Research On Partial Discharge Location For Bushings Using UHF Method

It is bushing faults that cause most of transformer unplanned outages. Overall, there are three main problems for partial discharge detection method of bushings:(1) the safety and reliability is low. (2) poor anti-interference ability and low signal-to-noise ratio. (3) Unable to realize fault location and diagnosis of partial discharge. For this purpose, on-line partial discharge (PD) detection method and TDOA location method based on ultra-high frequency (UHF) signals are presented.Firstly, According to the typical defects of the actual bushings, a non-partial discharge 110kV transformer bushing was taken as an object to design four PD physical models. And then the PD signals of different defects were detected by the pulse current method and the UHF detection method, through a lot of experiments and analysis of cumulative PD phase patterns (PRPD). The test results show that:the defects of bushings UHF phase patterns and pulse current method to measure the results remain the same, the defects have great differences in the patterns shape, phase distribution and the relative amplitude distribution. These features provide experimental basis for further development of pattern recognition of bushings type of discharge.Then, aimed at the key problems of bushings uhf partial discharge location, this paper illustrates the basic principle, which is based on time delay positioning The calculation is based on the three dimensional case Chan’s algorithm, using the superposition of small disturbance of the newton-raphson algorithm for locating calculation ehrsson; This paper presents a method of UHF signal delay for different parts of the discharge for bushings. Test results show that:(1) in the tests of bad connection in bushing tap,UHF signal correlation degree is high, the correlation analysis method has high stability, good accuracy;(2) in the tests of surface discharge on the bottom of bushing, both of the rise time and last time of UHF signals is longer, the minimum energy method has better stability, higher operation efficiency.The research is valuable and meaningful for on-line PD detection and location for bushings.