Integrated differential flow method for preventing voltage transformer differential protection unwanted operation
A differential protection and transformer technology, applied in emergency protection circuit devices, electrical components, etc., can solve the problems of transformer differential protection misoperation, large differential unbalanced current, and the influence of zero-sequence current cannot be eliminated
Active Publication Date: 2008-08-20
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 zone, there will be a large differential unbalanced current, and the ratio braking criterion, inrush current and over-excitation braking criterion cannot perform reliable braking, especially in transformers. When the load current is very small or even zero, the ratio braking criterion and inrush current braking criterion cannot perform braking. As long as the error current exceeds the threshold, the transformer differential protection will malfunction
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[0010] A comprehensive differential current method for preventing maloperation of transformer differential protection, which can be realized by the circuit of a comprehensive differential current brake device for preventing maloperation of transformer differential protection shown in FIG. 1 . 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 , 3i o After filtering by filter 01, 3I is obtained 0 , the output terminal of the filter 01 is connected to one 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 fundamental positive sequence filter The three input terminals of 1 respectively input the three-phase differentia...
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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 the ratio brake criterion, that is, the ratio of the differential current to the through current, to identify the fault outside the zone and the fault in the zone; at the same time, through the inrush current and over-excitation brake criterion, That is, by analyzing the waveform or harmonic content of the differential current, the excitation inrush current and the over-excitation current can be identified 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 trans...
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IPC IPC(8): H02H7/045
Inventor 徐习东
Owner ZHEJIANG UNIV