Discrimination method of magnetizing inrush current of transformer based on grille fractal

Abstract

The invention provides a discrimination method of a magnetizing inrush current of a transformer based on grille fractal, and is used for discriminating the magnetizing inrush current in time and protecting safety operation of the transformer and a power grid. The method includes following steps: (1) calculating the number of intersected square grilles during covering required by sampling signals in a sampling period deltat before a sampling moment tk, wherein the side length of the square grilles is delta; (2) locating catastrophe points of current signals by employing a grille fractal algorithm; (3) calculating a ratio R of the grille number at the sampling moment tk+1 to the grille number at the sampling moment tk; and (4) obtaining an R-value variation curve of the sampling signals, andproposing following criteria according to the difference between the magnetizing inrush current and an internal fault current on the R-value variation curve: determining that the sampling signals arethe magnetizing inrush current if a second maximum value point with higher value appears within 10 ms after the R-value has a first maximum value point, and otherwise determining that the sampling signals are the internal fault current. According to the method, the magnetizing inrush current can be discriminated in time to avoid damage to the transformer by the magnetizing inrush current.

Description

technical field [0001] The invention relates to the technical field of identification and discrimination of excitation inrush current, in particular to a grid fractal-based identification method for excitation inrush current of a transformer. Background technique [0002] With the construction of the global energy Internet, the voltage level and capacity of the transformers put into the power system are higher, and higher requirements are put forward for the transformer relay protection devices. As the most important electrical equipment in the power transformation link of the power system, the power transformer not only plays an important role but also has a large number, and is crucial to the entire power system. Moreover, transformer maintenance is difficult and takes a long time, resulting in huge economic losses. [0003] The main protection of oil-immersed transformers is generally composed of two parts: gas protection and current differential protection, among which ...

AI Technical Summary

Problems solved by technology

[0006] However, with the improvement of transformer manufacturing process and the increase of capacity and voltage level, many problems continue to appear in the existing schemes, such as the slow identification of excitation inrush current, the lack of universal adaptability to the criterion of excitation inrush current, and the distinction between internal fault current and excitation inrush current. The sensitivity is not high enough and the reliability of identifying the excitation inrush current is insufficient, etc.

Images