In China, the 10kV distribution network operates with neutral ungrounded. Due to the influence of high transition impedance and branches, the problem of fault location has not been effectively solved. The characteristics of C-type travelling wave method at neutral ungrounded system are analyzed in this paper. Multi-point fault location method based on C-type travelling wave method is proposed. By actively injecting high-voltage pulses into the circuit and using multiple measuring devices to detect the reflected wave of the fault point, the effect of high-impedance- grounded and branch points on the reflected wave of the fault point is effectively reduced, and the success rates of reflected wave detection of the fault point are improved. The validity of the method is verified by simulation.
The transmission line, as the faultiest device in power system, cross many complex areas which will cause worse work condition. This is, both the rate of faulty and the difficulty of the manual fault location are raised. While accurate fault location method could reduce the workload and outage cost, increase the speed of repairing and improve both the reliability and economics of power system. Therefore, it is essential for HVDC systems which have much longer transmission lines. The existing fault location device of HVDC transmission lines are based on the principle of transient travelling-wave. However, due to the interference caused by on-off of power electronic devices and signal resonances, the single-ended travelling-wave method can not be applied in HVDC. The characteristics of clutter interferences of HVDC system and the coupling between double pole lines are analyzed in paper. A novel single-ended travelling-wave fault location method for HVDC transmission lines based on the correlation between two pole lines is proposed. The signal of the non-fault pole line is applied as reference signal; the method suppresses interference through the cross-correlation calculation between the fault and the no-fault pole line. So the reflected wave is enhanced and the identification reliability of the reflected wave is improved. The validity of the method is verified by simulation and on-site data analysis.
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