Measurement of grounding resistor of
electric power system
Abstract：The paper describes the significance and necessity of measurement of grounding resistor of electric power system. It points out the shortcomings of traditional method. In order to overcome the disadvantage of it, we try to use a new method to measure grounding resistor intelligently , which add current power to measure and frequency analyse to get the result. We set up an automatic ,real-time ;online practical system based-on MCS-51 single chip control and disposal, it can get the radical waveform by FFT, which change signals from real field to frequency field .The system improve the precision and agility of grounding resistor testing. It makes a way come true that does not affect normal working of power system and improve measurement precision .It will bring great application value in electric power system.
The system hardware makes use of digital signal processing technique, synchronic data sampling technique to get the samples of current and voltage. Add current power to assist the measurement when current of neutral almost zero. Transmit data to PC by RSC-232 interface .
Its software uses system self-detecting algorithm to assure measurement channel .It uses softening hardware technique software synchronic data sampling to trace the frequency of exterior signal, in other words , it gives sampling control signals 128 times of power net's frequency .It uses Direct Digital Frequency Synthetics (DDFS) algorithm to transform radical sine waveform parameter table into needed current. It uses FFT algorithm to get radical waveform altitude of current ,voltage and resistor .
The system simulator and experimental results show the system reaches design request . The result also demonstrate the correctness and feasibility of the methods in the paper. It provides a practical application system with requisite gist and foundational condition.
Keywords: Grounding resistor、signal power、Fast fourier transforms (FFT)、Direct Digital Frequency Synthetics(DDFS)、singlechip
