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A single-phase grounding protection method for distribution network based on the straight line fitting direction of zero-sequence current mutation

A zero-sequence current and straight line fitting technology, which is applied in the direction of current indication, emergency protection circuit devices, electrical components, etc., can solve problems such as prominent interference signals, misoperation or refusal of protection devices, and eliminate high-frequency interference signals Effect of improving reliability, effect of high protection reliability

Active Publication Date: 2016-09-14
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

[0004] The invention provides a distribution network single-phase grounding protection method based on the straight line fitting direction of the zero-sequence current mutation, which is used to solve the impact of the existing single-phase grounding protection principle due to the small interference signal of the zero-sequence current, the influence of the compensation process and the The zero-sequence current of the non-fault line is greater than the sum of the zero-sequence current of other lines, which leads to the lack of malfunction or refusal of the protection device, so as to improve the reliability of the protection device

Method used

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  • A single-phase grounding protection method for distribution network based on the straight line fitting direction of zero-sequence current mutation
  • A single-phase grounding protection method for distribution network based on the straight line fitting direction of zero-sequence current mutation
  • A single-phase grounding protection method for distribution network based on the straight line fitting direction of zero-sequence current mutation

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Experimental program
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Embodiment 1

[0041] Embodiment 1: as figure 1 Shown is a 35kV distribution network composed of 6 feeder lines whose neutral point is grounded through an arc suppression coil. G in this network is an infinite power supply; T is the main transformer with a transformation ratio of 110 kV / 35kV, and the connection group is YN / d11; the distribution voltage side of the main transformer in my country's distribution network is generally connected in a triangle, and there is no neutral point in the system. When the system adopts the resonance grounding method, it is necessary to obtain a neutral point that can be grounded by the arc suppression coil. Adding a grounding transformer is The best way, here T Z It is a zigzag transformer specially used for grounding of the compensation grid; L is the arc suppression coil, and R is the damping resistance of the arc suppression coil. The line adopts three types of lines: overhead line, overhead line-cable hybrid line and cable line, and the numbers of the ...

Embodiment 2

[0047] Embodiment 2: as figure 1 In the distribution network system shown in which the neutral point is grounded through the arc suppression coil, the system parameters are the same as those in Embodiment 1. Now suppose the feeder L 2 A single-phase ground fault occurs in phase A at a distance of 4km from the busbar. The initial phase angle of the fault is 90°, the fault transition resistance is 20Ω, and the sampling frequency is 100kHz. The waveforms of bus zero-sequence voltage and feeder zero-sequence current in the 0.1ms time window after the fault are as follows: Figure 4 shown. Using the db4 wavelet to decompose the zero-sequence voltage of the bus and the zero-sequence current of each feeder with 6 layers of wavelets, the wavelet coefficients of the zero-sequence voltage wave of the bus and the zero-sequence current of each feeder in the frequency band of the power frequency in the 0.1ms time window after the fault are obtained. Figure 5 shown. The least square me...

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Abstract

The invention relates to a single-phase grounding protection method of a distribution network based on a straight line fitting direction of a zero-sequence current mutation amount, and belongs to the technical field of relay protection of electric power systems. For the resonant grounding system, when a single-phase grounding fault occurs in one of the feeders, the present invention firstly intercepts the zero-sequence voltage of the bus and the zero-sequence current of each feeder in the short time window after the fault and performs wavelet decomposition on it, and extracts the location of the power frequency respectively. The wavelet coefficients of the frequency band; then use the least square method to perform a straight line fitting on the extracted wavelet coefficients, and solve the slope value of each primary line; finally, the slope value of the primary line corresponding to the bus zero-sequence voltage and each feeder zero-sequence current The slope values ​​of the corresponding primary lines are multiplied. When the product is less than zero, it is determined that the feeder has a forward fault, and the protection element operates. When the product is greater than zero, it is determined that the feeder has a reverse fault, and the protection element does not operate. The invention has low difficulty in use and high protection reliability.

Description

technical field [0001] The invention relates to a single-phase grounding protection method of a distribution network based on a straight line fitting direction of a zero-sequence current mutation amount, and belongs to the technical field of relay protection of electric power systems. Background technique [0002] The distribution network covers a wide area and provides electricity services directly to users. According to statistics, single-phase ground faults account for about 80% of distribution network faults. The resonant grounding system of the distribution network is the neutral point grounding system through the arc suppression coil, which is a small current grounding system. The single-phase grounding fault of the small current grounding system will affect the non-fault phase ground voltage and cause it to rise, and the voltage rise will damage the insulation of the grid equipment; especially intermittent arc grounding will cause arc overvoltage, which will destroy ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/26G01R19/14
Inventor 束洪春高利黄文珍朱梦梦段瑞敏
Owner KUNMING UNIV OF SCI & TECH
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