Transformer interturn short circuit protection method based on current ratio variable quantity

Abstract

The invention discloses a transformer interturn short circuit protection method based on current ratio variable quantity. The method includes that a current ratio of the primary side of each phase winding to the auxiliary side is calculated according to current data which is obtained by collecting of a current transformer, then the current ratio variable quantity in two adjacent time is obtained, delay starting criteria are protected, opening protection delay is built, or the delay starting criteria are repeatedly protected, then operation conditions are protected to build a judgment, if the judgment is not built, the delay starting criteria are repeatedly protected, if the judgment is built, a transformer tapping is adjusted and judged, if the transformer tapping is not adjusted, a protective device can conduct action, and circuit breakers of all sides of the transformer are started aside, winding fault is cut off. The method is not influenced by three-phase current imbalance which is caused by an external fault of the transformer and other types of internal faults of the transformer, can improve sensitivity of the protection action, simultaneously has good selectivity, and therefore obviously improves correct action rate of transformer interturn short circuit protection.

Description

technical field [0001] The invention relates to an inter-turn short-circuit protection method of a three-phase transformer with a built-in winding transformer, in particular to a transformer inter-turn short-circuit protection method based on a current ratio variation, and belongs to the technical field of power main equipment protection. Background technique [0002] As the main electrical equipment widely used in the power system, the power transformer's safe operation is a necessary condition for the reliable operation of the power system. Traditional three-phase transformers generally adopt the dual configuration of differential protection and gas protection as the main protection. Among them, the current transformer of the traditional longitudinal differential protection is installed on the lead wire between the transformer and the circuit breaker. The current flowing through the differential relay is an unbalanced current when the transformer is in normal operation or ...

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Problems solved by technology

[0004] In view of the problem that the setting value of the differential protection in the existing transformer inter-turn short circuit protection is relatively high, but the protection measurement value of the inter-turn short circuit is low, and the protection cannot be effectively identified, the present invention provides a transformer based on the current ratio variation Inter-turn short-circuit protection method, which is not affected by the three-phase unbalanced current caused by external faults or other internal faults of the transformer, can improve the sensitivity of the protection action, and has good selectivity, thereby significantly improving the correctness of the transformer inter-turn short-circuit protection. action rate

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