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High-accuracy resonant grounding system single-phase earth fault line selection method

A single-phase grounding fault and resonant grounding technology, applied in fault location, fault detection according to conductor type, measurement device, etc., can solve the problem of affecting the accuracy of line selection, modal aliasing of EMD algorithm, small amplitude of high frequency components, etc. problem, to avoid modal aliasing, enhance amplitude, and ensure reliability.

Inactive Publication Date: 2018-03-06
TIANJIN UNIV
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  • Abstract
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  • Claims
  • Application Information

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Problems solved by technology

However, the amplitude of the transient signal is affected by many factors. In the case of a small fault closing angle, the amplitude of the high-frequency component is small. Only using the high-frequency component for line selection will affect the accuracy of line selection.
Moreover, there is no clear standard for the selection of wavelet basis functions, and the EMD algorithm may have the problem of mode aliasing

Method used

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  • High-accuracy resonant grounding system single-phase earth fault line selection method
  • High-accuracy resonant grounding system single-phase earth fault line selection method
  • High-accuracy resonant grounding system single-phase earth fault line selection method

Examples

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Effect test

example 1

[0026] Set outgoing line L 1 A single-phase ground fault occurs at a distance of 3km from the busbar, the fault closing angle is 0°, and the transition resistance is 10Ω.

[0027] After the fault occurs, the line selection algorithm is started, and the zero-sequence current sampling data of the half cycle before the fault and the 3 cycles after the fault are read.

[0028] Firstly, Ensemble Empirical Mode Decomposition (EEMD) is performed on the zero-sequence current sampling data of each outgoing line, and the signal is decomposed into several Intrinsic Mode Function (IMF) components and residual components to facilitate further fault feature extraction.

[0029]

[0030] In the formula: S(t) is the original signal; n is the number of IMF components; C i (t) is the i-th layer IMF component, where C 0 (t) is the remaining component. The intrinsic mode functions of different layers represent the components of the signal at different time scales.

[0031] Afterwards, the ...

example 2

[0049] Set the bus fault, the fault closing angle is 30°, and the transition resistance is 50Ω.

[0050]After the fault occurs, the line selection algorithm is started, and the zero-sequence current sampling data of the half cycle before the fault and the 3 cycles after the fault are read.

[0051] Firstly, Ensemble Empirical Mode Decomposition (EEMD) is performed on the zero-sequence current sampling data of each outgoing line, and the signal is decomposed into several Intrinsic Mode Function (IMF) components and residual components to facilitate further fault feature extraction.

[0052]

[0053] In the formula: S(t) is the original signal; n is the number of IMF components; C i (t) is the i-th layer IMF component, where C 0 (t) is the remaining component. The intrinsic mode functions of different layers represent the components of the signal at different time scales.

[0054] Afterwards, the Hilbert transform is performed on the IMF components of each layer and the re...

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Abstract

The invention relates to a high-accuracy resonant grounding system single-phase earth fault line selection method, which comprises the following steps: positioning fault moment, and reading zero sequence current sampling data of each line in half of a cycle before fault and three cycles after fault; carrying out ensemble empirical mode decomposition on the zero sequence current sampling data of each line; calculating instantaneous energy of Hilbert marginal spectrum of each line in a low-frequency band of 0-10 Hz and a high frequency band of above 250Hz, and selecting two lines, the energy ofwhich is the largest, as primary selection lines; carrying out Hilbert transform on the initial half-wave portion after fault of an intrinsic mode function IMF of each of the two primary selection lines, calculating an instantaneous frequency average value of each IMF, and selecting IMF components, the instantaneous frequency average value of which is higher than 250Hz, to reconstruct high-frequency components of the zero sequence current; and carrying out inner product on the high-frequency components of the two lines, if the inner product is negative, judging that the primary selection line,the energy of which is the largest, is the fault line, and if the inner product is positive, judging the fault is the bus fault, outputting a line selection result and ending line selection.

Description

technical field [0001] The invention belongs to the technical field of relay protection and power distribution network. It is a line selection method with high accuracy for single-phase grounding fault in resonant grounding system. Background technique [0002] The resonant grounding system is mainly used in my country's medium and low voltage distribution network. After a single-phase ground fault occurs in the resonant grounding system, the line voltage is still symmetrical and does not affect the power supply to users. The regulations stipulate that it can run for 1 to 2 hours with a fault, and the power supply reliability is high. [0003] After a single-phase ground fault occurs in the resonant grounding system, because the arc suppression coil generally adopts the overcompensation method, the zero-sequence current characteristics of the fault line and the non-fault line are not clearly distinguished, and the fault line selection is very difficult. [0004] At present...

Claims

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Application Information

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IPC IPC(8): G01R31/08G01R31/02
CPCG01R31/086G01R31/50
Inventor 李永丽宋金钊刘勇
Owner TIANJIN UNIV
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