Transformer differential current protection mis-operation preventing relay protection method

Abstract

The invention discloses a transformer differential current protection mis-operation preventing relay protection method. The method includes the steps that firstly, a direct current component <phi0> of phi phase currents on the high-voltage side of a transformer, a second harmonic component <phi2> of the phi phase currents and a fundamental component <phi1> of the phi phase currents are measured; current sampling values of the phi phase currents on the high-voltage side of the transformer at sampling moments are measured, wherein phi is equal to a phase A, a phase B and a phase C; a waveform asymmetry coefficient mu<phi> of the phi phase currents on the high-voltage side of the transformer is calculated, and then whether the formula shown in the specification is workable or not is judged, if yes, a protector sends blocking signals to phi phase current differential protection, and therefore mis-operation of phi phase current differential protection of the transformer is effectively prevented, wherein k<1> is a setting coefficient. According to the method, the transformer differential current protection mis-operation preventing function is achieved through summarized information of harmonic components of currents flowing into the high-voltage side of the transformer when the high-voltage side of the transformer is closed in a non-load mode, current differential protection mis-operation is effectively prevented when the high-voltage side of the transformer is closed in the non-load mode, and action reliability and safety of transformer differential current protection are improved.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a relay protection method for preventing maloperation of transformer differential current protection. Background technique [0002] When the high-voltage side of the transformer is closed with no load, the iron core of the transformer winding is saturated, and the current flowing into the high-voltage side is an excitation inrush current, which contains a certain amount of second harmonic components. In order to prevent the current differential protection from malfunctioning when the high-voltage side of the transformer is closed with no load , After the traditional current differential protection operates, it is opened or blocked by the second harmonic blocking criterion or the waveform discontinuity angle blocking criterion and then exported. If the transformer winding core is deeply saturated, the second harmonic content in the inrush current is ...

AI Technical Summary

Problems solved by technology

If the transformer winding core is deeply saturated, the second harmonic content in the inrush current is very small, and the discontinuity angle of the inrush current waveform is also very small, often smaller than the set threshold value, resulting in the second harmonic blocking criterion and the waveform discontinuity angle blocking judgment. According to the opening of the current differential protection outlet, the current differential protection malfunctions when the high voltage side of the transformer is switched on without load.

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