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P4-4 STUDY ON PULSE CURRENT OF TYPICAL PD MODELS IN POWER TRANSFORMER Guoli Wang Yanpeng Hao Yanming Li Xi’an Jiaotong University, Xi’an, 710049, P. R. China Abstract: In power transformer, partial discharge (PD) detection is an effective means for monitoring and evaluation of dielectric faults in an early stage of development. Traditional PD detection methods can not completely depict discharge mechanism of insulation system, so pulse current of PD should be investigated. In this paper, a broad band measuring system is developed and the high speed digital oscilloscope TDS680B is used to measure pulse current of PD. The whole setup is tested by the PD pulse of standard corona model. Then several typical PD defect models in power transformer are designed and these pulse current are measured by this system. Results show that, the PD pulse in oil is always instability and oscillatory. Moreover, for different models, the parameters of pulse are different, which can be made the reference of PD pattern recognition. Keywords: power transformer pulse parameter pulse current of PD INTRODUCTION PD activity is both a symptom of degradation in the insulating systems of power transformer and a stress mechanism which causes degradation. Over the years, many methods for detection of PD phenomena have been developed, the most common being acoustical, optical, chemical and electrical techniques[’]. Traditional PD detection is to measure and analysis the PD signals under 1 MHz, the PD characteristic of insulation system can not be completely depicted. In recent years, the ultra-wide-band (UWB) PD detection techniques have been put for~ard[*][~~[~]. Comparing with the traditional PD detection methods, it has many advantages, such as high sensitivity, anti- interference, large information and so on. To study the discharge mechanism and the discharge pattern recognition, the analysis of a single PD pulse should be emphasized. SIMULATING PD SOURCES In an oil-filled power transformer, because its configuration is complex, the discharge places and the discharge types may be various. Usually, the discharge types could be summed as following: 1) Discharge in oil gap existing in the oil-barrier insulation between windings; 2) Discharge in oil gap of the end windings; 3) Discharge in oil gap between the insulating wire and the insulating paper; 4) Partial discharge of oil-paper insulation; 5) Discharge in oil gap between turns; 6) Partial breakdown of inter-turn insulation; 7) Surface discharge of insulation paper.
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This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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