| Electronic current transformer is one of the important equipment for power system data acquisition.It can effectively compensates for the shortcomings of traditional electromagnetic transformers such as magnetic saturation,large volume,and difficult insulation.It is the inevitable choice for the development of digital substations.However,because its internal structure contains a large number of electronic components,it is seriously affected by electromagnetic interference in the actual operation.At present,the research on ECT electromagnetic compatibility performance test is not perfect,which leads to its operation without reasonable electromagnetic compatibility test.That results a lot of electromagnetic compatibility faults and electromagnetic compatibility problems in operation,which brings great risks to the safe and stable operation of the power system.Based on this,this paper makes a qualitative study on the electromagnetic interference mechanism of ECT in the actual operation of the substation,analyzes the electromagnetic interference sources,interference ways and restraining measures in the operation of ECT,and focuses on the analysis of the influence of the transmission and radiation interference caused by the serious interference source of the isolation switch for the ECT,through modeling and simulation.On this basis,in order to improve the stability of ECT hanging network operation,the open and capacitive small current test system of ECT isolation switch is designed according to the shortage of ECT existing electromagnetic interference performance tests,and the hardware and software of the system are analyzed and designed in this paper,which can realize the maximum assessment of the electromagnetic protection performance of ECT.Subsequently,the PC signal detection technology of the designed experiment is deeply studied in this paper.According to the characteristics of the merging unit output signal and the data acquisition system output signal by the host computer in the experiment,a signal detection method combining HHT with FFT is put forward,the high precision detection and analysis of the signal are realized.Firstly,aiming at the problems existing in the steady state signal analysis of FFT,the improved FFT high precision steady state signal detection method is studied.The four-spectrum-line interpolation FFT algorithm with four item five orders Nuttall window is studied,which has good interference resistance,and the spectrum leakage and fence effect can be effectively suppressed.So the high precision detection of amplitude,phase angle and frequency of steady state signal is realized.Secondly,in view of the endpoint effect problem of transient signal analysis in HHT,the improved HHT high precision transient signal detection method is studied.Through the improvement of the endpoint extension based on the slope,the impact of the endpoint effect is reduced effectively,and the high precision detection and analysis of the parameters of transient signal,the law of signal fluctuation and the time of disturbance are realized. |
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