Positive sequence synthesized brake device for preventing multiple-branch voltage transformer differential protection unwanted operation by utilizing fault components

Abstract

The invention discloses a positive sequence synthesized brake device for preventing multiple-branch voltage transformer differential protection unwanted operation by utilizing fault components, wherein the three-phase difference currents in the transformer differential protection constitute ratio braking element with the maximum value of zero-sequence current on each of the neutral point earthing end (or branches), when the positive input end signal is less than the negative input end signal on the comparators, the comparator outputs 0, the lateral area outer ground fault is determined, the three-phase differential protection exit is locked, otherwise the comparator 8 outputs 1, and the corresponding differential protection actuations are allowed. Tthe transformer differential protection accidental operation resulted from ground fault outside the lateral area when the errors of the three-phase current transformer are in inconformity.

Description

Technical field [0001] The invention relates to a transformer protection device, in particular to a fault component positive-sequence synthesis braking device for preventing the malfunction of the transformer protection. Background technique [0002] The existing differential protection devices for power transformers use ratio braking components, that is, through the ratio of differential current to cross current, to identify out-of-area faults and internal faults; at the same time, through inrush current and over-excitation braking components, that is, through analysis The waveform or harmonic content of the differential current can be used to identify the excitation inrush current and over-excitation current to achieve the purpose of identifying internal faults. For power transformers with neutral points directly grounded on two sides or above, when an out-of-area ground fault occurs on one grounded side, a large ground fault zero sequence current may occur on multiple sides. I...

AI Technical Summary

Problems solved by technology

However, when the errors of the three-phase current transformers on the grounding side are inconsistent, and the transformer only has power on the neutral point grounding side where an external fault occurs, the traditional method cannot eliminate the zero-sequence current caused by the external grounding fault on the neutral point grounding side. Influenced, there will be a large differential unbalanced current, and the ratio braking element and inrush braking element cannot perform reliable braking, especially when the transformer load current is small or even zero. The 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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