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Transformer excitation surge current identification method based on time-frequency characteristic quantities

A technology of time-frequency characteristics and excitation inrush current, applied in the direction of measuring electrical variables, instruments, measuring electricity, etc., can solve problems such as perfection, applicability to be improved, misjudgment, and difficulty in protection setting

Active Publication Date: 2013-11-27
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The protection setting of the above various principles is relatively difficult. In the application, the intelligence is set or corrected through experiments according to the actual situation, and there is a hidden danger of misjudgment.
Therefore, there are many kinds of excitation inrush current identification methods, but the degree of perfection and applicability still need to be improved.

Method used

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  • Transformer excitation surge current identification method based on time-frequency characteristic quantities
  • Transformer excitation surge current identification method based on time-frequency characteristic quantities
  • Transformer excitation surge current identification method based on time-frequency characteristic quantities

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0087] Implementation mode 1: figure 1 In the simulation system shown, the transformers are three single-phase three-winding transformers with Yd11 connection. The high-voltage winding connected to the 110kV system is the primary side of the transformer, and the medium-voltage winding and the low-voltage winding are cascaded to form the secondary side of the transformer. The transmission line is simulated by 5 sections of π-type equivalent circuit, each section is 4km long. The parameters of the transformer simulation system are shown in Table 1, and the parameters of the magnetization curve are shown in Table 2.

[0088] Table 1 Simulation system parameters

[0089]

[0090] Table 2 Magnetization parameters

[0091]

[0092] When a 30% turn-to-turn fault occurs inside the transformer:

[0093] (1) The differential current of the transformer is greater than the set value, and the data in the continuous 400 sliding time windows are decomposed by discrete wavelet deco...

Embodiment approach 2

[0097] Embodiment 2: The simulation system and transformer parameters are the same as Embodiment 1.

[0098] The transformer is closed with no load, and the closing angle is 45°. The calculation and statistics are carried out in the same way as in Embodiment 1. The expected value S=0.43>0.2, the excitation inrush current is correctly identified, and the protection is blocked. .

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Abstract

The invention relates to a transformer excitation surge current identification method based on time-frequency characteristic quantities, and belongs to the technical field of transformer relay protection. The method comprises the steps: if the differential current of a transformer is larger than a setting value, decomposing data inside continuous N sliding time windows by utilizing the discrete wavelet decomposition, respectively calculating the total energy Ej of differential currents inside the sliding time windows and the energy sum Edi of frequency bands of the sliding time windows, obtaining the energy percentage Eij of each sub frequency band inside one time window, and forming a characteristic matrix WTF. A correlation coefficient of integrated time-frequency characteristics of the sum inside two adjacent time windows is calculated. When is smaller than , the is equal to 1, or the is equal to 0. By utilizing the correlation coefficient for representing the time-frequency characteristics of different current signals and the change rules of the different current signals, the integrated correlation coefficient is combined to form an excitation surge current identification criterion. According to the transformer excitation surge current identification method based on the time-frequency characteristic quantity, by starting from the analysis of the differential current time domain and the frequency domain, the time-frequency characteristic differences between fault currents and excitation surge currents inside different sliding time windows are effectively found out, and compared with a traditional surge current identification method by utilizing a single characteristic quantity, the transformer excitation surge current identification method based on the time-frequency characteristic quantities has the advantages of integrating multiple pieces of information such as the amplitude, the phase, the singularity and frequency distribution of the differential current and having higher reliability.

Description

technical field [0001] The invention relates to a transformer excitation inrush current identification method based on time-frequency characteristic quantities, and belongs to the technical field of transformer relay protection. Background technique [0002] Transformer is an indispensable and important equipment in the power system to connect networks with different voltage levels, and its safe operation is directly related to whether the entire power system can work stably and continuously. There are many types of transformer protection. Among many types of transformer protection, longitudinal differential protection can better meet the requirements of selectivity, quick action, sensitivity and reliability in relay protection, and is the main form of transformer main protection. The longitudinal difference protection uses the difference between the primary side current and the secondary side current of the transformer as the differential current, and if the differential cu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/00
Inventor 束洪春张兰兰田开庆
Owner KUNMING UNIV OF SCI & TECH
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