Phase-splitting differential flow method for preventing voltage transformer differential protection unwanted operation

Abstract

The invention discloses a phase-splitting differential flow method for preventing voltage transformer differential protection unwanted operation, wherein 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 value is less than a setting value K, the corresponding differential current is judged to be the error current caused by the faults outside the area, brake the corresponding phase ratio differential protection, thus preventing the differential protection accidental operation of the transformer. 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 without influencing the correct actuation of the differential protection under the circumstance of in-area faults.

Description

technical field [0001] The invention relates to a transformer protection method, in particular to a phase-separated 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 el...

AI Technical Summary

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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