Research And System Design Of Single Phase To Ground Fault Line Selection For Low Voltage Network Based On Least Square Method

With the development of the national economy and the scale of the city,the power supply and distribution network mainly uses buried underground cable lines to improve the reliability of power supply and the beauty of urban construction.The cable lines are mainly buried in the dark and damp environment.Once they are squeezed and collided,the insulation is destroyed and the single phase grounding fault is caused.Especially for the power supply system with high safety and reliability of power supply,if the single-phase grounding fault occurs,we must quickly and reliably identify the fault line and remove it.The existing route selection principle is relatively mature,but many algorithms are complex and slow to process.So searching for a fast and reliable route selection method is very important for low-voltage power supply system with high quality of power supply.The main line selection methods at home and abroad are summarized,and the principle of various line selection methods is briefly analyzed and evaluated.Analysis of the single-phase grounding fault occurs,the system changes characteristics of the zero sequence current,grounding leakage current and zero sequence voltage first order derivative,and then proposes a least squares line selection according to the polarity of the fault line identification algorithm.Aiming at the single-phase grounding fault of low-voltage power supply network in multistage and multi area substations,the least squares parameter is used to identify the state of the line,then the logic judgement is made according to the status of the circuit,and it is screened whether the line is a fault branch or a normal branch.In order to further verify the rapidity and reliability of the method,a test platform was built under the existing laboratory conditions,and the hardware circuit of signal acquisition and conditioning circuit was designed and made to capture signals of zero sequence current and zero sequence voltage of each branch.Finally,a scheme of leakage protection system based on TMS320F2812 chip is proposed.