Localization And Anti-interference Technology Of Hign Frequency Partial Discharge In Transforme Based On Multi-terminal Coupling

High frequency partial discharge(PD)detection is an important means of on-line detection of power transformers.It has the advantages of convenient installation and implementation,wide detection frequency band,high sensitivity and large amount of information.The existing high frequency partial discharge(PD)on-line detection mainly obtains signals from the neutral point of transformer,the iron core and the ground wire of the clamp.But it cannot obtain the discharge information of the winding head,which is difficult to eliminate the influence of external common-mode interference.In addition,high amplitude narrowband interference exists in the field background noise,which seriously affects the effective extraction of PD pulse signal.Therefore,this paper proposes a partial discharge positioning anti-pulse interference method based on high-frequency multi-terminal synchronous detection and proposes an adaptive interference suppression method based on k-means clustering and kurtosis improved singular value decomposition for narrowband interference.The research contents and achievements are as follows:(1)Based on the 110kV three-phase double-winding solid transformer,a high frequency multi-terminal synchronous detection test research platform was built.Different pulse injection modes were used to simulate the external discharge interference,main insulation discharge,longitudinal insulation discharge and internal non-winding discharge of the transformer,and the characteristics of the multi-terminal coupling pulse signal under corresponding circumstances were studied.The results show that external interference discharge,internal winding discharge and non-winding discharge can be distinguished according to the amplitude,polarity and spectral energy of the winding head,neutral and shell detection signals.(2)Combined with the topological connection of the substation main transformer,a large number of test studies on 220kV and 500kV transformers are carried out by injecting double exponential pulses,and a method of multi-terminal discharge positioning and anti-interference is proposed by replacing the winding head signal with the ground line signal of the transformer’s adjacent equipment.Based on the linear method of energy ratio of winding first and end signals,the influence of transformer high-voltage leads on multi-terminal detection and positioning under online condition is studied.It is found that the propagation characteristics of high-frequency signals in transformer windings determine the slope of energy ratio straight line,and the external leads determine the intercept of energy ratio straight line.Then,the correction coefficient method of high-frequency pulse source positioning is proposed.The results show that this method can reduce the discharge positioning error to less than 8%.(3)Aiming at the periodic narrow-band interference problem of transformer high-frequency current local discharge signal,an adaptive narrow-band interference suppression method based on k-means clustering and kurtosis improved singular value decomposition is proposed.In this method,the sampled discrete high-frequency local discharge signal is constructed into a HANKEL matrix and the singular value decomposition is carried out.By extracting the first two singular values and reconstructing and calculating the kurtosis value,the narrowband interference can be determined in the discharge signal.Based on this,the eigenvalues such as singular value,singular entropy increment and standard difference of singular value subset are constructed to carry out 3D clustering.Narrowband interference is suppressed by multi-parameter automatic extraction of narrowband interference singular value reconstruction.The results show that this method can improve the signal-to-noise ratio of the measured signal by 1.95 times,which is better than the existing wavelet and empirical mode decomposition denoising methods,and realize the adaptive denoising under different narrow-band interference conditions in the field.(4)The partial discharge positioning and anti-interference device of transformer based on high-frequency current multi-terminal detection is developed.The high precision satellite B-code synchronous timing technology is used to realize the synchronous acquisition function of multi-channel high-frequency signals.An algorithm module of anti-interference and energy-ratio linear positioning for transformer multi-terminal on-line monitoring is developed,and a complete set of transformer high frequency station on-line monitoring,positioning and diagnosis system is formed.The topological structure test of 110kV、220kV and 500kV main transformer shows that the system runs stably,the positioning and anti-interference results are accurate.