Development Of The Precise Grounding Resistance Measuring Tester Based On The Method Of Selective Electrode

Along with the development of electric power system and the expansion of the scale ofpower grid, all kinds of microcomputer monitoring equipment general application, thedemand of the grounding device is more and more, and the resistance of the grounding devicesize is one of the major criteria for good grounding. Firstly this paper introduces thedevelopment and present situation of the grounding resistance measurement,then on the basisof analyzes of the traditional grounding measuring device and measurement methods, thevirtue and principle which is based on the frequency conversion method and the method ofselective electrode grounding resistance measurement are studied, moreover the designscheme of grounding resistance design which uses the combination of the frequencyconversion method and the method of selective electrode are puts forward.Secondly, the paper studies on the resistance measurements algorithm deeply.By usingfast Fourier transform (FFT) grounding resistance measurement, it’s hard to do synchronoussampling and integer period truncation, and it will also affect the accuracy of measurement bythe fence effect and frequency spectrum leakage which FFT resulting into. Through FFT addwindow interpolation can effectively eliminate the effect and improve the accuracy of thecalculation the frequency and amplitude of the voltage and current of grounding resistance.Based on the scheme design of the system and the research of the adding window in FFTinterpolation algorithm, this paper realizes the high precision grounding resistancemeasurement system for ADSP-BF504F core processor. The measurement system includeshardware realization and software realization. The hardware of the system is mainly composedof the sensor design module, front-end processing module, digital processing module, signalacquisition module, ADC module, man-machine interface module, etc; In addition, tofacilitate development and future upgrade, the system software is modular in design. The software of the system includes the initialization, A/D conversion, data acquisition, dataprocessing, keyboard displaying, the setting of the sine excitation and so on.Finally, the computer simulations and experiments aiming at the measurement and thealgorithm of the system are carried out. The result of simulations shows that through theimprovement of FFT algorithm, it effectively suppresses the influence by the fence effect andthe frequency spectrum leakage.The research methods of this paper can improve the accuracyof the measurement and has high practical value.