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Fault line selection method of distribution network based on empirical mode decomposition (EMD)

An empirical mode decomposition, distribution network fault technology, applied in the direction of the fault location, etc., can solve the problems of high sampling rate, high hardware equipment requirements, difficult technology implementation, etc., and achieve low hardware requirements, easy implementation, and short data length Effect

Active Publication Date: 2012-10-24
CHUXIONG POWER SUPPLY BUREAU OF YUNNAN POWER GRID CO LTD
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Problems solved by technology

This type of method can correctly select the line but requires a high sampling rate and has high requirements for hardware equipment, which is technically difficult to implement

Method used

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  • Fault line selection method of distribution network based on empirical mode decomposition (EMD)
  • Fault line selection method of distribution network based on empirical mode decomposition (EMD)
  • Fault line selection method of distribution network based on empirical mode decomposition (EMD)

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Embodiment Construction

[0034] Such as figure 1 As shown, set up overhead line L 1 A single-phase ground fault occurs at a distance of 10km from the bus, and the fault time t f =25ms, the transition resistance is 20Ω, the fault closing angle is 90°, the time window length is 10ms, and the sampling frequency is 10kHz.

[0035] (1) After a single-phase grounding fault occurs in the distribution network, when the zero-sequence voltage of the busbar is 15% higher than the rated phase voltage, the starting element starts immediately. According to the three-phase current of each line measured at the protection installation site, the zero sequence current of each line is obtained by using the Clark transformation matrix:

[0036] i j0 = i jA + i jB + i jC , J=1,2,3,4,5,6,

[0037] The zero sequence current waveform of each line is as figure 2 Shown.

[0038] (2) EMD decomposition of the zero sequence current of each line, the sampling frequency is 10kHz, the effective sampling sequence length is 100 points...

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Abstract

The invention relates to a fault line selection method of a distribution network based on empirical mode decomposition (EMD), belonging to the technical field of the relay protection of a power system. The fault line selection method provided by the invention comprises the following steps of: solving a zero-sequence current by utilizing the Clarke transformation theory according to the three-phase current of each line when the distribution network fails and a protection element starts, wherein the three-phase current of each line is measured at the protection mounting part; selecting a discrete zero-sequence current signal with the sampling sequence length of 100 dots, and carrying out EMD (Empirical Mode Decomposition) on the discrete zero-sequence current signal so as to acquire m IMF (Intrinsic Mode Function) components; respectively solving the absolute values of the m IMF components of the zero-sequence current of each line to acquire m absolute values of IMFt (i); and then, summing the m absolute values of IMFt (i) of the zero-sequence current of each line to acquire EMD energy Ei, wherein the line with the maximum Ei value is a fault line. By adopting the sampling frequencyof 10 kHz and the time window of 10 ms, the fault line selection method provided by the invention needs data shorter in length, has the advantages of low hardware requirements, easiness in technological implementation, stronger tolerance to transition resistance and stronger practicability and is free from interference influences.

Description

Technical field [0001] The invention relates to the technical field of power system relay protection, in particular to a fault line selection method for a distribution network. Background technique [0002] The distribution network is responsible for the task of directly supplying power to the majority of users. Its neutral point mainly adopts ungrounded, resistance grounded, and arc suppression coil grounding operations. Because of its low ground current during faults, it is called a small current grounding system . According to statistics, single-phase ground faults account for more than 80% of the distribution network faults. When a single-phase grounding fault occurs in a small current grounding system, the non-faulty phase-to-ground voltage will increase, which will damage the insulation of power grid equipment; if intermittent arc grounding occurs, it will cause arc overvoltage and threaten the insulation of the system, and then develop into an interphase or Multi-point ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/08
Inventor 杨昌武周丹冯俊宗阮绍忠汪滔周志新李刚李起荣陈继金
Owner CHUXIONG POWER SUPPLY BUREAU OF YUNNAN POWER GRID CO LTD
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