A New Approach For Fault Location In Distribution Network Based On Active Disturbance Technology

Due to the complex construction of distribution network, which is the terminal of distributing electric power to the users, phase-to-ground fault occurs easily and contributes to the big part of phase-to-ground fault. Single-phase-to-ground fault will cause more serious fault if it were not solved in time. So it is of great significance to measure fault distance of single-phase-to-ground fault in the resonant grounded system for both economy and safety.The current researches on fault location mainly focus on three aspects:fault distance measurement, signal-input location and fault section location. Fault distance measurement is a technique that uses electric parameters of faulted feeder to calculate fault distance. Signal-input location is a technique that tracks a specific signal, which is injected to faulted feeder, to locate the fault point. Fault section location is a technique that locates and insulates the fault section to recover the power of non-fault section.Arc-suppression-coil-ground neutral system is widely used in our country. In recent years, power electronic switch, for its controllability and promptness, is applied to switch Petersen-coil components, such as damping resistors and compensation capacitors. By controlling power electronic switches of Petersen-coil, a voltage and current signal will appear to measure system parameters. In this paper, a new approach of fault distance measurement for single-phase-to-ground fault of resonant grounded system is presented. When single-phase-to-ground fault happens, thyristors with opposite conduction will make the damping resistance of Petersen-coil quit operation to extinguish arc efficiently. At the moment, disturbing signals would be produced in the faulted feeder by making thyristors turn off instantaneously and can be extracted to locate fault.This paper analyses the generation of disturbing signals based on superposition principle and deduces the calculation formula of fault location in resonant grounded system based on active disturbance technology. In this approach, by controlling the controllable switch’s turn-off time, generation time and amplitude of disturbing signal will be adjustable, which can increase signal’s recognition and raise work efficiency. Because of abundant frequencies in disturbance, the method can get several fault distances under different frequencies to eliminate measurement error appearing commonly under single frequency.This paper uses simulated analysis and lab experiments to verify the validity of the method. Single-phase-to-ground fault is analyzed in simulation under different fault locations, grounding resistances and trigger angles. On this basis, this paper detects the disturbing signals and calculates fault distance. In the lab, this paper establishes experimental platform of resonant grounded system and designs the disturbing signal generator, which can control the damping resistance to generate the disturbing signal, to study fault location in different condition. The results of fault location in simulated analysis and lab experiments agree with correct fault distance, which confirms the effectiveness of the method. In conclusion, this paper provides a feasible method for fault location in the distribution network.