Distribution network cable-wire mixed line failure route selection method by utilizing relative energy

Abstract

The invention relates to a failure line selection self-adapting method for a mixed line of a distribution network line-cable by utilizing the relative energy of a characteristic frequency band. The method is as follows: when the instant value of the zero sequence value of a bus is out of limit, a failure line section device instantly starts and records waves; a morphological filter is used for carrying out filter pre-treatment on the transient zero-sequence currents of temporary state of each line; a wavelet packet is applied for decomposing, the characteristic frequency bands of the transient zero-sequence currents of temporary state of each line are confirmed, the component of a stable state and the information of other frequency bands are eliminated and the line selection margin is improved according to the view of energy maximizing; the sizes of the relative energies in the front 1/4 period and the last 1/4 period in the back period of the failure under the characteristic frequency bands are compared according to the principle that the capacitance and current of the failure line under the temporary state attenuates fast in the characteristic frequency bands, thus forming the criterion for failure line selection. Principle analysis and imitation show that the relative energy of the first 1/4 period and the last 1/4 period in the back period of the failure is utilized for realizing the line selection, thus amplifying the temporary characteristics of the failure, avoiding the effect of an intermittent corner on the accuracy of the line section caused by the saturation of CT. The method is accurate and reliable for line selection.

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 of a distribution network cable-line hybrid line using relative energy. Background technique [0002] With the rapid development of urban construction, the overhead lines in the distribution network have to be transformed into cables and into the ground due to the impact on urban development. Laying cables can not only increase the transmission capacity and reduce the outgoing line scale of the substation, but also reduce the operation and maintenance cost and construction difficulty per unit transmission capacity, which is beneficial to the beautiful appearance of the city. Due to the relatively large ground capacitance of the cable, after a single-phase ground fault occurs in the system, the transient quantity of the cable line is more abundant than that of the pure overhead line. Therefore, making full use of the tra...

AI Technical Summary

Problems solved by technology

Due to the resonant grounding system under the compensation of the arc suppression coil, the fault zero-sequence current may appear reversed, and the current transformer saturation cause

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