Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference

A technology of exciting inrush current and differential current, applied in electrical components, emergency protection circuit devices, etc., can solve problems such as uncertainty diversity, difficulty in judgment, and complexity of fault waveforms

Active Publication Date: 2014-03-26
KUNMING UNIV OF SCI & TECH
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Problems solved by technology

However, the second harmonic braking method has the following disadvantages: the excitation inrush current is a transient current, which is not suitable for the harmonic analysis method of the Fourier series
However, the inrush waveform is related to many factors, and it has uncertainty and diversity. It is difficult to judge the waveform symmetry; at the initial moment of the fault, the fault current is not a standard sine wave, and the diversity of fault conditions and the fault waveform must be considered in the actual system. complexity of

Method used

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  • Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference
  • Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference
  • Excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference

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Embodiment 1

[0060] Embodiment 1: A fast identification method for exciting inrush current based on the distance between adjacent points on the plane formed by the difference between adjacent orders of differential current. Get the three-phase differential current of the transformer, extract the three-phase differential current data recorded by the measurement unit, and obtain the first-order difference and second-order difference of each phase differential current through the three-phase differential current data; The first-order difference of the phase is divided into the vertical axis, and three planes are constructed; the sum of the squares of the distances of all adjacent points on the three constructed planes is calculated, and then the maximum value of the three sums of squares is calculated dist2 sum , and then find dist2 sum The standard deviation and average value of the squared distance between adjacent points of the corresponding phase; the obtained average value and standard d...

Embodiment 2

[0082] Example 2: Establish as figure 1 The simulation system model of transformer failure and excitation inrush current is shown, in which the transformers are three single-phase three-winding transformers, which adopt Yd11 connection method, connect its high-voltage windings to the 110kV system as the primary side of the transformer, and cascade the medium-voltage windings and low-voltage windings The secondary side of the transformer is formed, and the parameters of the equivalent double-winding transformer are as follows: rated capacity is 250MVA, rated transformation ratio is 110kV / 10.5kV, equivalent resistance is 0.002pu, and equivalent reactance is 0.08pu. Its magnetization parameters are shown in Table 1:

[0083]

[0084] Table 1

[0085] Assume that a 1.5% winding ground fault of phase A occurs on the low-voltage side of the transformer, and the sampling frequency is 1kHz. Under this model, dist2 A (n) and Th1 A The comparison diagram of (n) is as follows fig...

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Abstract

The invention relates to an excitation surge current fast identification method based on planar adjacent point distances formed by differential current adjacent order difference and belongs to the technical field of power system relay protection. When an internal fault or excitation surge current of a transformer occurs, a protecting measuring device starts immediately, a measuring unit measures the three-phase difference current of the transformer, the three-phase difference current data recorded by the measuring unit is extracted, and the first difference and the second difference of each phase difference current are calculated according to the three-phase difference current; the second difference of each of the three phases is used as a horizontal axis, the first difference of the corresponding phase is used as a vertical axis, and three planes are constructed; calculating the quadratic sum of all adjacent point distances on the three constructed planes, calculating the maximum value dist2sum of the three quadratic sum, and calculating the standard deviation and average value of the square of the adjacent point distance corresponding to dist2sum; performing integration on the obtained standard deviation and average value to obtain Th1sum, and comparing the dist2sum and the Th1sum to distinguish the internal fault and excitation surge current inside the transformer.

Description

technical field [0001] The invention relates to a method for quickly identifying inrush currents based on the distance between adjacent points on a plane formed by the difference between adjacent orders of differential currents, and belongs to the technical field of electric power system relay protection. Background technique [0002] At present, the main protection of the transformer is the longitudinal differential protection using the electrical quantity and the gas protection of the non-electrical quantity. Among them, the longitudinal differential 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 current exceeds a certain setting value, it is judged as an internal fault. Transformer differential protection is based on the steady-state magnetic circuit balance of the transformer. This balance may be broken during the transient process: in the case of trans...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/045
Inventor 束洪春曹璞璘高利魏萌
Owner KUNMING UNIV OF SCI & TECH
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