Method for identifying excitation surge current and internal fault of transformer

Abstract

The invention discloses a method for identifying excitation surge current and internal fault of a transformer, belongs to the technical field of power system relay protection, and is to solve the technical problem of identifying the excitation surge current and internal fault of the transformer in a power system. The method comprises the following steps: sampling current in a transformer differential circuit; carrying out absolute value taking and sorting operation and the like on a sampling data sequence, and calculating an equal square ratio R; if R is less than Rset, judging that the current current is an internal fault current, and starting differential protection; or otherwise, calculating a correction factor FC and a correction equal square ratio RC, and further identifying the current current according to whether RC is greater than Rset or not. The method for identifying the excitation surge current and the internal fault has the advantages of simple steps, small calculation amount, convenient engineering implementation and the like.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for identifying transformer excitation inrush current and internal faults. Background technique [0002] Transformers are vital electrical equipment in power systems. On the one hand, transformers are responsible for the transformation and distribution of electric energy, which is indispensable in the safe operation of power systems; on the other hand, large transformers are expensive and have strong economic attributes. Therefore, the safe and stable operation of the transformer must be guaranteed. [0003] In the power system, the transformer is generally equipped with longitudinal differential protection as its main protection. The basic principle of transformer longitudinal differential protection is Kirchhoff's current law: the current flowing into the transformer is equal to the current flowing out during normal operation. However,...

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Problems solved by technology

However, most of these methods only distinguish the inrush current from the internal fault current in sinusoidal form, and are less involved in the saturated fault current (especially the saturated fault current caused by CT saturation when the transformer is put into the transformer with fault no-load), which may easily cause CT saturation. The saturation fault current in the case is misjudged as an exciting inrush current, resulting in false blocking of the transformer protection

Therefore, the current identification method of excitation inrush current is not perfect enough, and it is still necessary to study new and effective identification methods to improve the correct rate of transformer protection action

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