Positioning Research, Transformer Internal Partial Discharge Based On Ultrasound Technology

Partial discharge (PD) activity inside power equipment is an important reason to degrade electrical insulation and lead particularly to the failure of the equipment, and it is an important symptom of insulation status in power equipment. The international and domestic institutions have established corresponding standards and many token parameters to evaluate its damage to insulation, e.g. apparent charge, however these test parameters which express the insulation status of electrical equipments are sorely influenced by its site in devices, and it's difficult to exactly estimate the device's insulation status only by these test parameters, so it is important to locate the PD sources quickly and exactly. Whereas the conventional PD location methods, including electrical and ultrasonic location method, disable to do this very well, so it is necessary to research PD location to acquire better location theory and technique.In this paper, the propagation characteristics of ultrasonic emitted from PD are studied theoretically, and the interferences and suppression measurements are discussed. Based on these a new PD ultrasonic detection system has been developed to investigate the characteristics of PD models. This combinational way of software and hardware to pre-process the receiving ultrasonic signals demonstrates the capacity to suppress noise and interferences efficiently.The PD location method based on ultrasonic sensor array is described in this paper , whose basic principle is that firstly the acoustic pressure in each array element of three windings in transformer is obtained by calculating and analyzing these complex ultrasonic sound field , supposed PD position as a source of ultrasonic wave, simultaneously establishing an accurate database, and then matching the measured results with the database to get the geometric position of PD, consequently the precise positioning of PD in the transformer is achievedThe characteristics of this new approach are that firstly it can precisely locate the PD position in the transformer, secondly it can finish non-contact measurement of PD signals avoiding the the impact of tank for PD signal propagation ,thirdly it can test in high degree of automation, moreover, the size of sensor is so small that it may be put inside of transformer tank to measure at non-electric and non-contact style with no effect on the equipment itself.The investigation of PD location method based on ultrasonic sensor array is the important scientific and technological issue extracted from power generation, operation and equipment manufacture including of a number of disciplines and a wide range of technology and integrated cross-applications, such as physics and acoustics electrical ,modern antennas and digital signal processing technologies cross-disciplines etc.. Research and application of this project is of significance to insulation monitor of power facility, knowing PD effect on electrical insulation, locating PD position at an early date, and improving on maintain technological advances and strategies of power equipment.