Transformer excitation inrush current identification method based on skewed distribution of absolute value of sampling sequence

Abstract

The invention discloses a transformer excitation inrush current identification method based on the skewed distribution of the absolute value of the sampling sequence. The steps include: sampling the differential current of the differential protection of the transformer at a set sampling frequency; After the absolute value calculation, take the sampling data of the latest power frequency cycle and calculate its skewness coefficient; if the calculated skewness coefficient is greater than 0, it is determined that the differential current is an excitation inrush current; otherwise, it is determined that the differential current is not an excitation inrush current . The invention has the advantages of clear criterion, small amount of calculation, clear distinction, rapid and accurate action, low requirement on the hardware of the device, no manual setting of values, and convenient realization.

Description

technical field [0001] The invention relates to the technical field of transformer relay protection, in particular to a transformer excitation inrush current identification method based on the skewed distribution of the absolute value of a sampling sequence. Background technique [0002] Transformers are very important electrical equipment in power systems. Power transformers in power grids often have huge capacity and are expensive to manufacture. Relay protection devices must be used to ensure their safe and reliable operation. The longitudinal differential protection has high sensitivity and good selectivity, and it is often used as the main protection of transformers in engineering. However, the longitudinal differential protection of the transformer needs to avoid the unbalanced current flowing through the differential circuit. [0003] When the transformer is turned on with no load or the voltage recovers after the external fault is removed, a large inrush current may...

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Problems solved by technology

In addition, the inrush has the characteristics of a peak wave. Although the derivative at the peak is also zero, because it is a peak wave, the derivative changes sharply, and the sampling points will be relatively sparse; it can also be confirmed from the mechanism, because the inrush peak wave is ultimately a It is transmitted by the sinusoidal signal through the nonlinear excitation curve, and the slope of the excitation curve becomes very small after the inflection point, forming the peak wave of the inrush current, so the sampling point at the peak wave of the inrush current can be regarded as the dispersion (or dilution) of the sampling point of the sinusoidal signal ), the sampling point distribution of the inrush signal at the peak wave is naturally relatively sparse

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