Research On Single-phase Ground Fault Line Selection Method Based On Frequency Domain Parameter Identification

Most of China’s distribution network adopts neutral point non-effective grounding operation mode.When single-phase ground fault occurs,the fault current is weak and the arc is unstable,which makes the fault line selection difficult.In this paper,a single-phase ground fault line selection method based on frequency domain parameter identification principle is studied.When establishing a zero-sequence network with single-phase ground fault,the line is equivalent to a lumped-parameter π model with unequal capacitance values between the bus-side and load-side ground.According to the basic principle of frequency-domain parameter identification,in the case of knowing line models and parameters,the frequency domain parameter model of the external fault occurred on the line was established,and the related frequency domain equations were solved by the least squares method.Considering that the basic matrix pencil algorithm has low computational accuracy when the signal-to-noise ratio is low,this paper combines the singular entropy increment and the matrix pencil algorithm to form a matrix beam algorithm based on singular entropy to fix order,and using this algorithm to accurately extract the frequency information of the fault signal.Then,the phase-frequency characteristics of the zero-sequence network of each type of line under non-fault conditions and the phase-frequency characteristics of the mixed-line centralized parameter model under fault conditions are compared to determine the special frequency band,and the equivalent model of the line in the special frequency band is determined.By selecting the frequency point information in the special frequency band to calculate the capacitance parameter of the line near the load side,and the line selection criterion combining the transient information and the steady information is constructed according to the nature of whether the equivalent model changes during the fault process of the faulty line and the regular line,thereby achieving the accurate selection of faulty lines.Through the ATP,a radiation-type power supply network of the distribution network was built to simulate single-phase ground faults of overhead lines,cable lines and cable-line hybrid lines under different network structures,different transition resistances,different fault locations and different fault initial phase angle conditions.The data processing is carried out by using MATLAB to verify the single-phase ground fault line selection method based on frequency domain parameter identification.The simulation results show that the line selection method studied in this paper is correct and effective,and has strong adaptability and fault tolerance.