Transformer zero-sequence overcurrent protection method based on zero-sequence current phase space distribution center of gravity amplitude change

Abstract

The invention provides a transformer zero-sequence overcurrent protection method based on a phase-space distribution gravity center magnitude change of zero-sequence current. The method comprises thesteps of obtaining a zero-sequence current sequence I0 measured by a neutral line current transformer (TA) of a transformer at a certain sampling rate; judging whether a zero-sequence current amplitude is greater than a zero-sequence overcurrent protection action setting value or not, if so, starting a novel method provided by the invention, or else, continuously discriminating an inequality; carrying out normalization processing on the zero-sequence current, extracting a maximum value and a minimum value of the current within a determined time window, carrying out amplitude compression on various points in the sequence on the basis of the maximum value and the minimum value and obtaining the normalized zero-sequence current sequence, thereby making various points in the current sequence fall in a change range of [-1, 1]; carrying out phase-space reconstruction on the normalized zero-sequence current sequence I0' and obtaining a gravity center sequence G and a distance sequence R froma gravity center to an original point after a criterion is started; and judging a formula that R is greater than Rset is true or not. According to the method provided by the invention, zero-sequence overcurrent protection misoperation caused by excitation inrush current and restorative inrush current generated during no-load closing and external fault removal can be effectively prevented.

Description

technical field [0001] The invention discloses a zero-sequence overcurrent protection method for a transformer based on the variation of the gravity center amplitude of the zero-sequence current phase space distribution, and relates to the field of transformer zero-sequence overcurrent protection. Background technique [0002] The zero-sequence overcurrent protection of the transformer is the backup protection for the ground fault of the grid side winding, the grid side lead wire and the bus bar when the neutral point of the transformer is directly grounded, and the backup protection for the ground fault of the adjacent transmission line. [0003] At the moment of transformer charging and when external faults are removed, zero-sequence overcurrent protection malfunctions sometimes occur. For example, in June 2011, when the converter transformer of Baoji The current protection malfunctioned, causing the DC system to be blocked. In June 2006, a failure occurred in the 500kV Lu...

AI Technical Summary

Problems solved by technology

The peak value of the zero-sequence current can be reached considerably, which will cause the zero-sequence overcurrent protection to malfunction

And, obviously, none of the aforementioned blocking methods can effectively block the zero-sequence overcurrent protection

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