The Research And Realization Of Single-phase Grounding Fault Location About Distribution Networks Based On FFT

The distribution networks mostly adopt neuter point not- valid grounding in China, which is called the small current grounding system. The fault in distribution networks mostly is single-phase grounding fault because of its complex structure. The fast and accurate location that the single grounding fault, not only to the repair wire and promise dependable power supply, and circulate to the safe stability and economy that promises the whole electric power system to all have a very important function.The low frequency AC signal injection method applies effectively and widespread in distribution network single phase-to-grounding fault location. Traditional"S"injection method with 220Hz injected frequency is affected by the wires distributed capacitance, so low frequency method adopts 60Hz instead of 220Hz. The low frequency method uses dichotomy along the route to detect the fault, and its detector displays the real-time current waveform of the current position. Due to the outdoor environment factors, it's difficult to judge the present current distributed capacitance current or the fault current through the real-time waveform. The signal detector is designed systematically in the paper. The hardware part includes filter and amplification circuit, control section and display section, using Protel to draw boards with single chip 8051f310 and the filter UAF42. The software part includes the design of microcontroller A/D part, timing counter part, disruptions and spectrum analysis, with Keil C to complete part program compiles work.A FFT algorithm is used to analyze the detected current signal's spectrum in the paper. After compared the energy content with the power signal and the injected signal, the fault point can be judged by showing the two signals'energy content.