Magnetically balanced series transformer zero sequence differential protection method and device

Abstract

The invention provides a magnetically balanced series transformer zero sequence differential protection method and a magnetically balanced series transformer zero sequence differential protection device, which consider the current characteristics of a balance winding when a slight turn-to-turn fault occurs in the series transformer area, and construct differential protection based on a magnetic balance principle. Current transformers are installed on a grid side winding, a valve side winding and the balance winding of the series transformer, self-generated zero-sequence currents of the currenttransformers are calculated, differential currents are selected from the self-generated zero-sequence currents and serve as calculation quantities, and the slight turn-to-turn fault of the transformer windings can be reflected sensitively. The magnetically balanced series transformer zero sequence differential protection device can reflect the slight turn-to-turn fault in the series transformer area sensitively by taking comparison situations of the self-generated zero-sequence currents of the balance winding, a rated current of the balance winding and the zero-sequence currents of the otherwindings, effectively prevents protection malfunction when an external fault occurs, and can be widely applied to the series transformer containing the balance winding.

Description

technical field [0001] The invention relates to the technical field of differential protection of series transformers in the field of power systems, in particular to a zero-sequence differential protection method and device for magnetically balanced series transformers. Background technique [0002] The series transformer is one of the core components of the new FACTS (Flexible AC Transmission Systems, flexible AC transmission system) equipment, and it is at the core of the exchange between the DC valve and the AC transmission line. Due to the special operating environment requirements of the series transformer, the series transformer needs to adopt a special design structure and manufacturing process. In addition, the electrical characteristics of series transformers during normal operation are also different from those of ordinary parallel transformers. [0003] When the FACTS system is in light-load operation, the terminal voltage at both ends of the series transformer w...

AI Technical Summary

Problems solved by technology

However, if the characteristics of the current transformers on each side used in the field are poorly consistent, zero-sequence differential current may still occur, and there is a risk of zero-sequence differential protection misoperation

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