Study On The Oriented Coupling System Of On-Line Monitoring Partial Discharge In 1# Transformer Of Qijiang Power Station And Analyzing The Result Of Application

On-line PD monitoring of power transformer is presently the research hotspot in the area of high voltage insulation measurement and diagnosis. Due to the weakness of PD signals and bigness of interferences, the extraction of Pd pulses faces many difficulties. The developed techniques, with some achievement, have not met the demand of engineering application yet.The paper proposes an on-line monitoring system of PD in transformers. And according the demand of engineering, the data derived from the system, which reflect the characteristic of PD in transformers, are analyzed.Firstly, theoretic and simulation research work is carried out on resonant nonmagnetic core Rogowski coil current sensor, which is usually used in PD monitoring of transformer. The equivalent circuit of sensor was designed and its transfer function was obtained through theoretically analysis. Using software Saber, the effects of coil number, parallel connection capacitance and loading resistance on the frequency responses of PD signals and the sensitivity was studied; Taking the locale application into account, the safety and reliability of the current sensor under the large power current and lightning pulse current was ensured.Secondly, the hardware and software of the on-line monitoring system of PD in transformers are designed. The on-site current sensor, filtering-amplifying circuit and signal sampling circuit are developed on our own; the software system completes the functions of the high-accuracy signal sampling, the convenient and fast data inquiring and the safe and stable transiting of data.Finally, the whole system achieves to fix on the 1# main transformer of Qijiang Power Station, to operate in test and to conclude the characteristic of PD in 1# main transformer by analyzing the PD data derived from system. The situation of operating in test suggests: the system, which is capable to attain the functions of sampling and analyzing PD information and extracting the characteristic of PD, is safe and stable and is satisfied with the demand of engineer application.