Multifunction realization of active electronic current transformer
In order to fit for the urgent requirement of the digital substation, the research of electronic current transformer (ECT) attracts more and more attention. The multifunction of ECT is especially studied in order to expand its application range. In this paper, a type of active ECT is introduced firstly. The redundant backup design of high-voltage circuit is presented after that. It will be greatly helpful for the improvement of stability and reliability of active ECT. The multifunction of lowvoltage side circuit is also discussed carefully. The local display, harmonic analysis and remote communication between ECT and master computer are all designed and realized. Therefore, the application field of active ECT will be expanded significantly. The validities of above circuits are all illustrated in Lab at last.
Analysis on Reliability of Electronic Current Transformer Based on Failure Modes,Effects Analysis and Fault Tree Analysis
Reliability analysis is the key procedure during the development of electronic current transformer (ECT). On the basis of the contrastive analysis on reliability of electromagnetic current transformers, by means of failure modes and effects analysis (FMEA) as well as fault tree analysis (FTA) the reliability of a kind of electronic current transformer is researched, and perfect worksheets of both FMEA and FTA are established. All of minimum cut sets of fault trees are found out and the qualitative analysis on the reliability of the ECT is conducted. The effectiveness of the presented reliability analysis method is verified by the results of the analysis on two practical examples during the development and test process of the ECT.
Realization of high precision harmonics analysis with pleisiochronous DFT arithmetic
This article introduced a kind of pleisiochronous Discrete Fourier Translation (DFT) algorithm to realize the high precision harmonic analysis when there would be a non synchronization between the sampling period and the signal period. First, the paper proposed the high precision equalizing value calculation process of the periodic functions by using the pleisiochronous algorithm when the sampling would be non synchronous. Then through a newly constructed function, the Fourier translation process was converted to the solution procedure of an equalizing value of a periodic function. Further more, the quasi synchronous algorithm and Fourier translation algorithm were integrated. After the discretization, the high precision harmonic analysis algorithm routine, which would be suitable for computer processing, was obtained under non synchronous condition. The simulating test shows that the accuracy of the integrated algorithm is higher than that of DFT by one order. When the deviation of the sampling periods is less than half period and the sampling number required by the sampling theorem is satisfied, after properly selecting the parameters of the algoritm, the measuring accuracy of nearly “perfect synchronized sampling” can be got.