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A Transformer Inrush Current Identification Method Based on Differential Current Gradient Angle Approximate Entropy

A technology of excitation inrush current and differential current, applied in the direction of measuring electrical variables, instruments, measuring electricity, etc., which can solve the problems of lost signal distribution and inability to reflect the complexity of signal sequences.

Active Publication Date: 2018-01-12
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a transformer excitation inrush current identification method based on the approximate entropy of the differential current gradient angle, by performing first-order difference and gradient angle processing on each phase difference current, and finally obtaining the method used to measure the signal Sequence complexity and the dimensionless numerical value that characterizes signal characteristics—approximate entropy, overcome the existing inrush current identification method that loses information in the signal distribution pattern during signal processing and cannot reflect the complexity of the signal sequence in terms of structural distribution, etc. lack of

Method used

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  • A Transformer Inrush Current Identification Method Based on Differential Current Gradient Angle Approximate Entropy
  • A Transformer Inrush Current Identification Method Based on Differential Current Gradient Angle Approximate Entropy
  • A Transformer Inrush Current Identification Method Based on Differential Current Gradient Angle Approximate Entropy

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Experimental program
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Effect test

Embodiment 1

[0076] Example 1: Establish as figure 1 The transformer excitation inrush current simulation system model is shown, in which the transformers are three single-phase three-winding transformers, which adopt the Yd11 connection method, and connect its high-voltage windings to the 110kV system as the primary side of the transformer, and the medium-voltage windings and low-voltage windings are cascaded to form a transformer On the secondary side, the parameters of the equivalent double-winding transformer formed are as follows: the rated capacity is 250MVA, the rated transformation ratio is 110kV / 10.5kV, the equivalent resistance is 0.002pu, and the equivalent reactance is 0.08pu. Its magnetization parameters are shown in Table 1.

[0077] Table 1 Magnetization parameters of transformer core

[0078]

[0079] Now assume that the no-load closing fault occurs in the transformer at 0.5s, and the simulation time is set to 1s. The initial phase angle of the fault is 0°, the samplin...

Embodiment 2

[0085] Example 2: Establish as figure 1 The parameters of the transformer internal fault simulation system model shown are described in detail in Embodiment 1, and will not be repeated here.

[0086] Now assume that the single-phase ground fault of phase A occurs on the transformer in 0.5s, and the simulation time is set to 1s. The initial phase angle of the fault is 0°, the sampling rate is set to 5kHz, the transition resistance is set to 0.001Ω, and the grounding resistance is set to 1Ω. Under this model, the simulation results are as follows: Figure 4 As shown, the sequence of gradient angles required 20ms after the internal fault occurs is as Figure 5 shown.

[0087] Under this model, select the differential current data within the 20ms time window after the fault, calculate the differential current, first-order difference, gradient angle and standard deviation of each phase according to the sequence described in this patent, and use the approximate entropy algorithm t...

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Abstract

The invention relates to a transformer excitation inrush current identification method based on differential current gradient angle approximate entropy, belonging to the technical field of electric power system relay protection. When an internal fault occurs in the transformer or an excitation inrush current is generated, measure the three-phase differential current of the transformer and obtain the absolute value of the differential current of each phase, calculate the absolute value of the first-order difference of the waveform of the absolute value of the differential current of each phase at each sampling point, and calculate the absolute value of each phase The gradient angle approximate entropy of the first-order differential absolute value sequence, and the maximum approximate entropy of each phase obtained as the criterion feature quantity, by comparing the criterion feature quantity with the preset threshold value, the internal fault of the transformer and the excitation inrush current are discriminated . The invention compares the difference between the power frequency sinusoidal waveform and the excitation inrush current waveform after a fault, has better robustness, and is still applicable when the initial fault waveform cannot be collected.

Description

technical field [0001] The invention relates to a transformer excitation inrush current identification method based on differential current gradient angle approximate entropy, which belongs to the technical field of electric power system relay protection. Background technique [0002] At present, the main protection inside the transformer is the differential protection using the electrical quantity at both ends. It constitutes protection based on the change of the current difference at both ends of the transformer's incoming and outgoing lines: when the differential current exceeds the preset setting value, it is judged as an internal fault. Since the differential protection principle is applicable to pure current elements that satisfy Kirchhoff's law, and the transformer differential protection does not include its excitation branch, it may cause its non-linear excitation branch during the no-load closing of the transformer or the removal of external faults. If the circuit...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/00
Inventor 束洪春魏萌高利曹璞璘
Owner KUNMING UNIV OF SCI & TECH
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