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Integrated differential flow method for preventing voltage transformer differential protection unwanted operation

A differential protection and transformer technology, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as inability to eliminate zero-sequence current, misoperation of transformer differential protection, large differential unbalanced current, etc.

Active Publication Date: 2004-12-29
ZHEJIANG UNIV
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Problems solved by technology

But when Y 0 The errors of the three-phase current transformers on the side are inconsistent, and the transformer is only in the Y 0 When there is power on the side, the Y cannot be eliminated by traditional methods 0 Due to the influence of the zero-sequence current caused by the ground fault outside the side area, there will be a large differential unbalanced current, and the ratio braking element, inrush current and over-excitation braking element cannot perform reliable braking, especially in the transformer load current When it is very small or even zero, the ratio braking element and inrush braking element cannot brake this. As long as the error current exceeds the threshold, the transformer differential protection will malfunction

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  • Integrated differential flow method for preventing voltage transformer differential protection unwanted operation

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Embodiment 1

[0011] A comprehensive differential current method to prevent maloperation of transformer differential protection, which can be achieved by figure 1 A circuit of a comprehensive differential current braking device to prevent maloperation of transformer differential protection is realized. The device is composed of filter 01 , fundamental positive sequence filter 1 , filter 2 , multiplier 3 and comparator 4 . Among them, the input terminal of the filter 01 is input to the transformer Y o side zero-sequence current instantaneous value signal 3i o , its output terminal is connected to an input terminal of the multiplier 3; the other input terminal of the multiplier 3 inputs the setting value K, and its output terminal is connected to the negative input terminal of the comparator 4, and the three of the fundamental positive sequence filter 1 The three input terminals respectively input the three-phase differential current instantaneous value signal i da i db i dc , the output...

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Abstract

The invention discloses an integrated differential flow method for preventing voltage transformer differential protection unwanted operation, wherein the base wave positive sequence current or negative sequence current of the three-phase difference currents in the transformer differential protection constitute ratio braking element with the zero-sequence current on the Y0 side, when the ratio of the base wave positive sequence current or base wave negative sequence current and zero-sequence current is less than a setting integer K, the Y0 lateral area outer ground fault is determined, The advantage of the invention is, the transformer differential protection false operation resulted from neutral ground lateral area outer earth fault can be fully prevented.

Description

technical field [0001] The invention relates to a transformer protection method, in particular to a comprehensive differential current method for preventing maloperation of transformer differential protection. Background technique [0002] The existing power transformer differential protection device uses a ratio braking element, that is, through the ratio of differential current and through current, to identify external faults and internal faults; at the same time, through inrush current and overexcitation braking elements, that is, through Analyze the waveform or harmonic content of the differential current to identify the inrush current and over-excitation current to achieve the purpose of identifying internal faults. to Y 0 / Δ wiring power transformer, in order to prevent Y 0 The zero-sequence current of the ground fault outside the side area causes the differential protection to malfunction. At present, Y 0 The method of transforming the side three-phase current elim...

Claims

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Application Information

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IPC IPC(8): H02H7/045
Inventor 徐习东
Owner ZHEJIANG UNIV
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