PD Location System In Transformer Based On LabWindows_CVI By Ultrasonic Measurement

Large power transformers are one of the main operating equipment,of which insulation monitoring plays a pivotal role in stable security operation of network.Partial discharge(PD) is one of the main reasons of electrical equipment insulation aging.Transformer online PD detection and localization can discover defects to avoid major accidents.Ultrasonic positioning method is a strong anti-jamming capability,convenient and economical way to locate PD source.However,due to the actual situation,the measured PD signal has many interference and the internal structure of transformer is complex,which makes effective extraction of partial discharge signals and pinpoint partial discharge source become a problem.Positioning research results use UHF PD positioning method more,however this method not only the high cost and difficult to obtain accurate signal difference, it is difficult to pinpoint the source of PD.By analyzing the domestic and international line partial discharge detection technology, proposed and developed partial discharge ultrasonic signal positioning system based on virtual instrument in transformers,and verify the effectiveness of the system through several experiments. Details are as follows:Firstly, the importance of transformer partial discharge detection and expounded the current research are introduced.Researched and analysis the partial discharge principle of transformer and discharge process,and depth studied the ultrasound theory and principles of ultrasound to detect partial discharge,laid the theoretical foundation for the system design.Secondly, combined with knowledge of ultrasonic testing,analyzing the observed PD signal and its noise reduction methods,based on PD signal and its noise characteristics,author proposes using independent component analysis based band-pass filter and empirical mode decomposition method for cutting back partial discharge signal noise,and analyze the effect of this method by Matlab simulation,the results show that the method works well.Then through analysis the the arrival time difference location method,key point were found as signal delay between the PD signal.Analyzed The basic algorithm of difference between the acquisition time,the classic generalized cross-correlation algorithm is used as the acquisition method of delay,and doing the Matlabsimulation,and the result shows that the method works well to get signal delay.Finally,the virtual instrument technology and system configuration are introduced in detail.Selected LabWindows_CVI virtual instrument development platform to design a PD ultrasonic positioning software system.hardware setting,signal acquisition,noise reduction,data storage,and three-dimensional positioning PD source can be done,including displaying all user interfaces. The function of the system is verified by experimental platform, the experiment proved that the system works well in filtering and positioning.