Fault detecting method for side windings of three-phase three-winding transformer

Abstract

The invention discloses a fault detecting method for side windings of a three-phase three-winding transformer. First, three-phase winding voltage and three-phase winding currents of two Y sides of the transformer are measured, the ring current of a delta side of the transformer is measured, and the zero-sequence voltage and the zero-sequence current of the two Y sides of the transformer are respectively calculated; the zero-sequence voltage and the zero-sequence current of the two Y sides of the transformer are converted to the delta side of the transformer according to a corresponding transformer ratio, the leakage inductance corresponding to mutual leakage flux of the two Y sides of the transformer is converted to the leakage inductance of the delta side according to the square of the transformer ratio, the leakage inductance corresponding to the mutual leakage flux of the delta side and the two Y sides of the transformer is converted to the leakage inductance of the delta side according to the square of the transformer ratio, and the resistance of the two Y sides of the transformer is converted to the resistance of the delta side according to the square of the transformer ratio; the leakage inductance corresponding to the natural leakage flux of the two Y sides of the transformer is calculated and converted to the leakage inductance L'2 and leakage inductance L'3 of the delta side and the leakage inductance L1of the delta side self of the transformer; L1, L'2, L'3 and setting threshold values L1 set, L2 set and L3 set form fault detecting criterions for the side windings of the three-phase three-winding transformer.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a fault detection method for side windings of a three-phase three-winding transformer. Background technique [0002] 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 △ / 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 △ side or convert the current of the △ side to the two groups of Y sides to eliminate the imbalance. current. In order to eliminate...

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Problems solved by technology

Since the 220kV side of the 220kV three-phase three-winding transformer is connected to the 500kV power grid, the 110kV side of the 220kV three-phase three-winding transformer is connected to the 110kV power grid, and the 10kV side of the 220kV three-phase three-winding transformer is connected to the 10kV distribution network, when the current differential protection When a fault is detected in the three-phase three-winding transformer, all circuit breakers on the three sides of the three-phase three-winding transformer will be tripped. Caused unplanned blackout of 10kV distribution network, affecting the normal production of social industry and agriculture

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