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Method for fault line selection of cable-wire mixed line of electric distribution network by using wavelet energy relative entropy

A wavelet energy, fault line selection technology, applied in the fault location and other directions, can solve the problem of loss frequency band fault characteristics, large differences in line distribution parameters and frequency-dependent characteristics.

Active Publication Date: 2011-06-08
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

Due to the large difference in line distribution parameters and frequency-dependent characteristics of cable lines and overhead lines, the frequency bands with the most concentrated energy of each line are not necessarily the same. feature

Method used

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  • Method for fault line selection of cable-wire mixed line of electric distribution network by using wavelet energy relative entropy
  • Method for fault line selection of cable-wire mixed line of electric distribution network by using wavelet energy relative entropy
  • Method for fault line selection of cable-wire mixed line of electric distribution network by using wavelet energy relative entropy

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Embodiment 1

[0086] Example 1: figure 1 System shown, line L 6 At 2km away from the busbar, the fault closing angle is 60°, the transition resistance is 200Ω, and a single-phase ground fault occurs. Use 10kHz sampling frequency to record waves, and get the zero-sequence current waveforms of the fault line and each healthy line before and after the 1 / 4 cycle of the fault, as shown in image 3 as shown, image 3 The zero-sequence current waveform of the middle fault line is marked in the figure, and the rest are the zero-sequence current waveforms of each healthy line.

[0087] Using db10 wavelet pair image 3The 1 / 4 cycle data of the zero-sequence current of each line shown is analyzed by multi-resolution, and according to the formulas (1) to (4), the energy distribution of the zero-sequence current of each line in each frequency band is obtained as follows: Figure 4 shown. Figure 4 The energy of the zero-sequence current of the faulty line in each frequency band is marked in the fig...

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Abstract

The invention relates to a self-adaptive method for fault line selection of a cable-wire mixed line of an electric distribution network by using full-band wavelet energy relative entropy. The method comprises the following steps: when the zero-sequence voltage instantaneous value of a bus is out of limit, starting a fault line selection device immediately; performing wavelet decomposition on zero-sequence current in 1 / 4 cycle after the fault of each line, performing single reconstruction on wavelet decomposition coefficients under each scale, and calculating the wavelet energy under each bandof the zero-sequence current of each line by using reconstruction coefficients; and calculating the wavelet energy relative entropy under each band of each line and solving the comprehensive wavelet energy relative entropy of each line by combining the super-strong recognition capability of the relative entropy to slight differences between signals, and self-adaptively selecting out the fault line by comparing the size of the full band comprehensive wavelet energy relative entropy of each line. Theoretical analyses and a large number of emulations show that the method effectively avoids the influence caused by a CT saturation discontinuous angle on the line selection, and is applicable to the cable-wire mixed lines, pure cable lines and pure aerial lines.

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 distribution network cable-line hybrid lines using wavelet energy relative entropy. Background technique [0002] With the development of the distribution network, the proportion of cable lines in the resonant grounding system is increasing. When a single-phase ground fault occurs in a resonant grounding system, the ground capacitance of the cable line is large, and the transient quantity is more abundant than that of the pure overhead line. Making full use of the transient characteristics of the cable-line mixed line for line selection can greatly improve the line selection efficiency. reliability. [0003] When a single-phase ground fault occurs in the resonant grounding system, the line voltage is still symmetrical and the fault current is small, which has little impact on the power supply of the load. The regul...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/08
Inventor 束洪春彭仕欣孙士云刘可真唐岚刘志坚孙向飞邱革非杨毅常勇单节杉刘永泰
Owner KUNMING UNIV OF SCI & TECH
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