Method for measuring circulating current in triangular winding of transformer

Abstract

The invention belongs to the technical field of power system relay protection, and discloses a method for measuring circulating current in a triangular winding of a delta / Y / Y wiring transformer. The method comprises the following steps of: measuring two groups of Y-side three-phase winding voltages ua2, ub2 and uc2 and two groups of Y-side three-phase winding currents ia3, ib3 and ic3 of the delta / Y / Y wiring transformer; establishing a mathematic model of the relation among delta side circulating current and the two groups of Y-side three-phase winding voltages and currents according to a loop equation of the delta / Y / Y wiring transformer; and calculating the delta side circulating current in real time. According to the method, measurement of the delta side circulating current can be realized without using any delta side current mutual inductor, the current differential protection of the transformer can be realized by using an obtained result of the circulating current, current phase calculation is not required, the influence of unbalanced current caused by the delta side circulating current on the current differential protection acting performance of the delta / Y / Y wiring transformer is eliminated in principle, and the reliability of the current differential protection action of the delta / Y / Y wiring transformer is improved.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for measuring circulating current in a delta-shaped winding of a Δ / Y / Y-connected transformer. Background technique [0002] 110kV and 220kV transformers widely used in power systems usually use three-phase three-winding transformers. In order to ensure that the phase potential is close to the sine wave and provide a path for the third harmonic, a set of windings of the three-phase three-winding transformer must be connected in delta, so its connection method is Δ / Y / Y connection. [0003] The current differential protection is the main protection of the transformer. In order to make the current differential amount zero during normal operation, it is necessary to convert the current of the two groups of Y sides of the transformer to the Δ side or convert the current of the Δ side to the two groups of Y sides to eliminate the imbalance. curre...

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Problems solved by technology

However, because the transformer circuit equation of the Δ / Y / Y connection transformer is too complicated, the above three types are only applicable to the Δ / Y connection transformer and cannot be applied to the calculation of the delta winding circular current of the Δ / Y / Y connection transformer. Therefore, At present, there is still a lack of an effective method to obtain the delta winding circular current of the Δ / Y / Y connection transformer, so as to improve the operation reliability of the current differential protection of the Δ / Y / Y connection transformer, so as to realize the discrimination of the transformer excitation inrush current based on the equivalent instantaneous inductance The popularization and application of the method in Δ / Y / Y connection transformer

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