Turn-to-turn zero-sequence differential protection method and device for valve side winding of series transformer

Abstract

The invention provides a turn-to-turn zero-sequence differential protection method and device for the valve side winding of a series transformer. The turn-to-turn zero-sequence differential protectionmethod comprises the following steps: firstly calculating the starting threshold value and braking coefficient of zero-sequence differential current, then determining zero-sequence differential current starting criterions and valve side winding turn-to-turn zero-sequence differential protection criterions, and finally judging whether valve side winding turn-to-turn zero-sequence differential protection is of actions. In the turn-to-turn zero-sequence differential protection method for the valve side winding of the series transformer provided by the invention, when a small turn-to-turn fault occurs in the valve side winding, under the premise that the protection of a unified power flow controller is free of action, turn-to-turn protection can be accurately and rapidly acted, rapid isolation of the turn-to-turn fault of the valve side winding is guaranteed, the valve side winding is avoided from being damaged, and safe operation of the series transformer is guaranteed.

Description

technical field [0001] The invention relates to the technical field of relay protection, in particular to a method and device for zero-sequence differential protection between turns of a valve side winding of a series transformer. Background technique [0002] As the transmission corridors of the power system become increasingly saturated, it will become more and more difficult to increase the transmission capacity by building new transmission lines. The needs of large-scale interconnected networks to increase the transmission power of the power grid and reduce losses have become urgent problems that need to be solved. Unified Power Flow Controller (UPFC) is a new generation of flexible AC power transmission equipment with the most comprehensive functions so far. The application in actual engineering has obvious technical advantages and broad application prospects. [0003] The series transformer is an important part of UPFC. Its valve-side winding is connected to the conve...

AI Technical Summary

Problems solved by technology

[0005] In order to overcome the defect that the inter-turn fault of the valve side winding of the series transformer cannot be reliably isolated due to the insufficient sensitivity of the longitudinal differential protection in the above-mentioned prior art, the present invention provides a zero-sequence differential protection method and device for the valve side winding of the series transformer , first calculate the zero-sequence differential current starting threshold and braking coefficient, then determine the zero-sequence differential current starting criterion according to the zero-sequence differential current starting threshold, and determine the zero-sequence difference between turns of the valve side winding according to the braking coefficient Finally, according to the zero-sequence differential current starting criterion and the zero-sequence differential protection criterion between the turns of the valve side winding, it is judged whether the zero-sequence differential protection between the turns of the valve side winding operates. The zero-sequence differential protection has high sensitivity, and the small turn-to-turn fault of the valve side winding of the series transformer can be quickly and reliably isolated

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