Research On On-line Monitoring Device And Algorithm Of Dielectric Loss Factor For 220kV Current Transformer

Power supply system of electric traction is an important part of the electric railway, which is composed of overhead lines and traction substation and provides electrical energy for electric locomotive. Current transformer (TA) is an important part of the traction network control loop, once a fault occurs, it will seriously affect the safe operation of the substation. In order to improve the operation reliability of current transformer, the paper researches and develops an online monitoring device for current transformer. The subject researches on 220kv current transformer of Xinxiang power supply section of Shijiazhuang-Wuhan high-speed railway of Zhengzhou Railway Bureau. Study and design of the on-line monitoring device for the running state of the 220kV dry current transformer for high speed railway traction power supply equipment.Firstly, this paper deeply studies the internal structure of dry high voltage current transformer and the principle of monitoring. The dielectric loss factor, leakage current and insulating capacity is chosen as on-line monitoring parameters. The paper analyzes the relationship between the physical meaning and the failure of the equipment. Discuss how to realize the accurate monitoring of monitoring quantity stability in the complex environment of substation further. Through the comparison and analysis, the method of harmonic analysis is used as a basic method for the calculation of the dielectric loss factor. Through analyses various factors causing errors, improve the method of harmonic analysis. Firstly, the collected data are processed by analytic transformation. Put forward a high accuracy estimation algorithm for harmonic analysis method. The algorithm is that DFT transform with Hanning window to signal and use the energy centrobaric method for correction. At the same time, the dielectric loss factor was further modified by the dynamic window algorithm. The algorithm is following the frequency fluctuation of power grid and adjusting window length dynamically, so that the sampling is more close to the full period, sampling. Through theoretical derivation and simulation of MATLAB, comparing with other algorithm for dielectric loss factor, proved that this method is more accurate and the computation is smaller than before.In order to realize that online monitoring of current transformer is stable and reliable. On-line monitoring device for 220kV current transformer is designed and made. We select TMS320F28335DSP as the processor of the device. Through the data collection, data analysis, data storage, display the data and limit alarm in the last. This paper completes the hardware design of the device and the program design based on the above algorithms, and test operation of the equipment under laboratory conditions. At last, the device is tested on the spot, and the waveform and operation data are collected for a period of time. The results show that the device is stable and can meet the requirements of the on-line monitoring of dry type high voltage current transformer insulation.