Fault line selection method for resonant grounded power distribution system by pattern spectrum

Abstract

The invention provides a fault line selection method for a resonant grounded power distribution system by pattern spectrum. When the resonant grounded power distribution system has a single phase fault, the zero sequence current of each line can be increased suddenly; and at the instant of the fault, the direction of the zero sequence current of a fault line is opposite to that of a perfect line; therefore, the zero sequence current of each line is subjected to multi-scale morphological operation firstly, and then the pattern spectrum of the zero sequence current is derived; after the fault line has a fault, the pattern spectrum of the first-half wave zero sequence current is mainly distributed in the positive scale, while after the perfect line has a fault, the pattern spectrum of the first-half wave zero sequence current is mainly distributed in the negative scale; therefore, positive scale spectral values and negative scale spectral values of the pattern spectrum of the zero sequence current of each line are respectively summed, and then a ratio of the sum of the positive scale spectral values to the sum of the negative scale spectral values of the zero sequence current of each line is respectively calculated; and a line with the maximum ratio is the fault line, otherwise, the bus fault is judged. The method has strong antijamming capacity, is not influenced by fault close angle and transition resistance, has low requirement on sampling frequency of signals, and has the advantages of convenient realization and low cost.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a fault line selection method for a resonant grounded power grid using a form spectrum. Background technique [0002] When a single-phase ground fault occurs in the resonant grounded power grid, the line voltage is still symmetrical and the fault current is small, and it can continue to run for 1 to 2 hours, which is conducive to improving the reliability of power supply. However, the non-fault relative ground voltage rises, and long-term operation will easily cause the fault to expand into a two-point or multi-point short circuit; arc grounding will also cause overvoltage in the entire system, endangering the insulation of the equipment and the safe operation of the system, so the fault line must be determined in time , troubleshoot as soon as possible. However, the grounding phenomenon of the resonant grounding power grid is very complicated. Whe...

AI Technical Summary

Problems solved by technology

The line selection method based on steady-state quantities is easily affected by transition resistance and unstable arc, has low sensitivity, and is prone to misjudgment

The signal injection method uses the method of injecting external signals into the system for line selection, but it has the following obvious disadvantages: ① When grounded through high resistance, the injected signal is weak and difficult to detect; Interference; ③The applicable voltage level is low (usually 10kV), and the operation and maintenance workload is relatively large. When a single-phase grounding occurs in the resonant grounding grid, the capacitor of the faulty phase is discharged and the capacitor of the non-faulty phase is charged, resulting in a higher amplitude than the steady-state value Transient current several times to dozens of times larger

The line selection method based on transient quantities has high sensitivity and is less affected by the arc suppression coil, but the line selection effect is mostly unsatisfactory. The main performance is that the line selection has little protection desire, low accuracy and reliability.

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