Identification method of transformer excitation inrush current based on kurtosis and skewness

Abstract

The invention discloses an identification method for excitation surge current of a transformer based on kurtosis and skewness. The identification method comprises the following steps: initially setting a first setting value, a second setting value and a third setting value, performing uniform continuous sampling on differential current of the transformer by adopting an assigned sampling frequency to obtain a sampling value sequence; if a current effective value of the differential current is smaller than the first setting value, exiting the procedure, and otherwise, aiming at the current sampling value sequence, calculating the kurtosis and the skewness of the differential current of the latest power frequency cycle; if the kurtosis is greater than the second setting value and the skewness is greater than the third setting value, judging that the transformer is in an operation state of the excitation surge current, and locking differential protection of the transformer, otherwise, judging that the transformer is in other non-excitation surge current operation states; returning to continuously process the current effective value of the differential current. The identification method disclosed by the invention has the advantages of obvious criterion distinguishing degree, high correctness of identification result, low requirement on hardware realization, short judgment time, good real-time property and low requirement on hardware of an implementation device.

Description

technical field [0001] The invention relates to the field of electrotechnical technology, in particular to a transformer excitation inrush current identification method based on kurtosis and skewness. Background technique [0002] The power transformer is one of the most important electrical main equipment in the power system, and its reliable operation is directly related to the safety and stability of the entire power grid. However, the correct operation rate of transformer relay protection in my country has been low for a long time. According to relevant literature statistics, the current correct operation rate of 220kV transformer differential protection is less than 80%, which is far lower than the operation level of other equipment protection. There is an urgent need for transformer differential protection. Performance is further improved and improved. Transformer excitation inrush current and internal fault identification are inherent and unavoidable core issues of tr...

AI Technical Summary

Problems solved by technology

[0006] (2) When the three-phase transformer is closed with no load, the excitation current waveform of each phase is basically the same as that of the single-phase transformer, and they are all biased to one side of the time axis, but a symmetrical inrush may occur in a certain phase

For a three-phase transformer, although a symmetrical inrush current may appear in one phase, at least one phase of the inrush current is asymmetrical, and its skewness is greater than 1

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