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T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis

A technology of wavelet coefficient and correlation analysis, applied to electrical components, emergency protection circuit devices, etc., can solve the problems of linkage protection failure, unpredictable compensation voltage phase change, refusal to operate, etc., to improve accuracy, improve reliability, reduce risk effect

Active Publication Date: 2015-03-04
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For the T-connection line, the feedback from the three ports to the T-contact will make the phase change of the compensation voltage unpredictable, so the setting of the relay action threshold becomes very difficult, and there are occasional cases of malfunction and refusal. occur
At present, the more common directional components also include positive sequence fault component directional relays, negative sequence fault component directional relays, zero sequence fault component directional relays and directional impedance relays. The performance is different from the application in ordinary lines. The mutual cooperation between the components in each direction becomes more difficult due to the complex structure of the T-connection line. In some cases, the linkage protection will even fail.

Method used

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  • T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis
  • T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis
  • T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] Example 1: Establish as figure 1 The T-connection grid line model shown. In the system, the line length l MN = 120km, l TQ = 80km, l PM =70km. It is stipulated that the positive direction of the current is that the busbar points to the line. Now assume that a phase A metallic ground fault F occurs on the line MT 40km away from the M terminal 1 , the fault initial phase angle is 90°, and the sampling frequency is 20kHz. By the M-terminal directional element R 1 , N-terminal directional element R 2 and Q-terminal directional element R 3 The voltage and current transient quantities in the 0.5ms time window after the fault are obtained as follows: Figure 2-7 shown. The 8-layer wavelet decomposition is performed on it, and the wavelet basis function is selected as db4, and the wavelet coefficients of voltage and current mutations in the first scale are obtained as follows: Figure 8-10 shown. Obtained by correlation analysis, the correlation coefficient r u,i_M...

Embodiment 2

[0039] Embodiment 2: The same T-connection grid line model as Embodiment 1. Now assume that a phase A metallic ground fault F occurs at 20km away from the N terminal on the TN section line 2 , the fault initial phase angle is 90°, and the sampling frequency is 20kHz. Respectively by the M, N, Q terminal directional element R 1 , R 2 , R 3 Obtain the transient quantities of voltage and current within the time window of 0.5ms after the fault, and perform 8-layer wavelet decomposition on it, and select the wavelet basis function as db4, and obtain the correlation coefficient of the wavelet coefficients of voltage and current mutations at the first scale as r u,i_M =-0.9960, r u,i_N = -0.9984 and r u,i_Q =-0.9984, satisfy - 1 ≤ r u , i _ ...

Embodiment 3

[0040] Embodiment 3: The same T-connection grid line model as Embodiment 1. Assume that a phase A metallic ground fault F occurs at a distance of 20km from the M terminal on the PM section of the line 4 , the fault initial phase angle is 90°, and the sampling frequency is 20kHz. Respectively by the M, N, Q terminal directional element R 1 , R 2 , R 3 Obtain the transient quantities of voltage and current within the time window of 0.5ms after the fault, and perform 8-layer wavelet decomposition on it, and select the wavelet basis function as db4, and obtain the correlation coefficient of the wavelet coefficients of voltage and current mutations at the first scale as r u,i_M =0.9999, r u,i_N = -0.9998 and r u,i_Q =-1, not satisfied - 1 ≤ r u , i ...

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Abstract

The invention relates to a T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis and belongs to the power system relay protection technical field. The method comprises the following steps that: transient state quantities of three groups of fault voltage and current are obtained through directional elements of R1, R2 and R3 at an M, N and Q end when a single-phase grounding fault occurs on a T-connection power grid; the transient state quantities of the voltage and current 0.5ms after the fault are respectively intercepted, and 8-scale wavelet decomposition is performed on the transient state quantities; wavelet coefficients of the transient state quantities of the voltage and current under the first scale are correspondingly selected so as to be subjected to correlation analysis; and when three groups of correlation coefficients are simultaneously greater than or equal to -1 and are smaller than or equal to -0.8, the fault is determined as an intra-cell fault, otherwise, the fault is determined as an extra-cell fault. As indicated by a large number of simulation experiments, the method is greatly applicable to T-connection power grid AC transmission line protection.

Description

technical field [0001] The invention relates to a protection method for a transient quantity unit of a T-connected power grid by utilizing the wavelet coefficient correlation analysis of voltage and current mutation quantities, and belongs to the technical field of electric power system relay protection. Background technique [0002] The ever-increasing scale of the power system and the continuous improvement of the voltage level put forward higher requirements for line protection. The shorter and faster time to remove faults is the relentless pursuit of relay protection. When a fault occurs in the power system, fault components from power frequency to high frequency will be generated. These high frequency components contain a lot of information, such as the type, location, direction, degree and duration of the fault. The effective extraction and application of these information has become an important means to improve the performance of relay protection, and the use of tran...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/26
Inventor 束洪春高利
Owner KUNMING UNIV OF SCI & TECH
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