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Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device

A technology of excitation inrush current and detection method, which is applied to measurement devices, circuit devices, emergency protection circuit devices, etc., can solve the problems of decay time that may reach tens of seconds, intermittent excitation inrush current waveform, etc., to ensure reliable operation, avoid interference, Accurate effect

Active Publication Date: 2014-03-26
SIEMENS AG
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Problems solved by technology

Furthermore, the excitation inrush current contains a large number of DC components and high-order harmonic components, and its waveform is mostly biased to the side of the time axis, and the waveform of the excitation inrush current may be discontinuous
In addition, the attenuation characteristics of the inrush current are related to the time constant of the transformer
The excitation inrush current generally decreases to no more than 0.25 to 0.5 times the rated current after 0.5 to 1 second, but for large-capacity transformers, the total decay time may reach tens of seconds

Method used

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  • Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device
  • Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device
  • Excitation surge current detection method, excitation surge current brake method and excitation surge current detection device

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Embodiment Construction

[0024] Various embodiments of the present invention will be described below with reference to the accompanying drawings. The above-mentioned advantages of the present invention will be more easily understood through the following description.

[0025] Figure 1A~1C Typical waveforms of magnetizing inrush currents appearing on three AC phases a, b and c of a three-phase transformer are exemplarily shown. By studying the waveform characteristics of the inrush current and referring to Figure 1, it can be concluded that the inrush current has the following characteristics.

[0026] (1) When the transformer is closed with no load, whether the inrush current is generated and the size of the inrush current are related to the phase angle at the time of closing. The excitation inrush current is the largest when the closing phase angle α=0 and α=π.

[0027] (2) Since there is a 120° phase difference between the three-phase voltages, the three-phase inrush currents will not be the same...

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Abstract

The invention discloses an excitation surge current detection method and device. The method comprises the following steps: obtaining differential current ix(n) of each alternating-current phase of a transformer; for the alternating-current phase, based on the differential current sampled in a cycle, calculating at least two factors (Ax(n), Bx(n)) used for waveform symmetry judgment; for each factor, obtaining a maximum value of three factors corresponding to three alternating-current phases as a maximum phase factor of the factors; based on the obtained maximum phase factor, calculating a corresponding waveform symmetry coefficient kmax by a waveform symmetry judgment algorithm; if the waveform symmetry coefficient kmax meets the waveform asymmetry requirement, determining that excitation surge current is generated.

Description

technical field [0001] The present invention generally relates to transformer protection technology, in particular to a method and device for detecting an excitation inrush current generated when a transformer is switched on with no load, and a braking method and device for an excitation inrush current. Background technique [0002] In the power system, when the transformer is switched on without load, there will be a momentary high current, for example, 6~8 times the rated current of the transformer. This instantaneous large current that occurs when the transformer is switched on is what is called "magnetizing inrush current" in the field. Therefore, when the transformer is switched on without load, the appearance of the inrush current may mistakenly trigger the differential protection action of the transformer, so that the transformer will automatically trip immediately after the switch is switched on. [0003] The main reason for the occurrence of "excitation inrush curr...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R19/165H02H7/045
CPCH02H1/043H02H7/045G01R19/0053G01R19/10G01R25/00
Inventor 秦雷鸣李锦辉杨敏高迪军陈卫陈德树饶纯
Owner SIEMENS AG
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