A Protection Method Based on Optical Transformer for Internal Asymmetric Fault of Generator

Abstract

The invention discloses an optical transformer-based internal asymmetric fault protection method for a generator. Three-phase currents of a generator terminal side of the generator and three-phase currents of a neutral point side are measured by an optical transformer respectively; a protection device calculates the following parameters: (1) a real part, a virtual part and an effective value of a negative-sequence current of a generator terminal; and (2) the real part, the virtual part and the effective value of the negative-sequence current of a neutral point respectively; and an internal asymmetric fault of the generator is judged and protection acts quickly than tripping when the three conditions are simultaneously met as follows: (1) the negative-sequence current of the generator terminal is greater than a constant value; (2) the negative-sequence current of the neutral point is greater than the constant value; and (3) the rear part of the vector ratio of the negative-sequence current of the generator terminal to the negative-sequence current of the neutral point is smaller than 0. The method has the advantages that (1) the constant value of each negative-sequence current only needs to avoid an unbalanced current during normal operation and the protection has relatively high sensitivity; and (2) a saturation problem does not exist in the optical transformer, the difference in an internal fault and an external fault is relatively obvious and the protection has relatively high sensitivity.

Description

technical field [0001] The invention belongs to the field of relay protection of power systems, and in particular relates to an optical transformer-based internal asymmetric fault protection method of a generator and a corresponding relay protection device or monitoring device. Background technique [0002] At present, the internal faults of generators are mainly reflected by longitudinal differential protection and longitudinal zero-sequence voltage protection. Longitudinal difference protection can only reflect phase-to-phase short-circuit faults, but not stator-turn-to-turn faults, and due to the influence of current transformer saturation, anti-maloperation measures need to be taken; while longitudinal zero-sequence voltage protection has relatively low sensitivity, and it is generally difficult to reflect stator branch open welding Fault. The invention utilizes the unique advantage that the optical transformer has no saturation problem, uses the optical transformer to ...

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Problems solved by technology

Longitudinal difference protection can only reflect phase-to-phase short-circuit faults, but not stator-turn-to-turn faults, and due to the influence of current transformer saturation, anti-maloperation measures need to be taken; while longitudinal zero-sequence voltage protection has relatively low sensitivity, and it is generally difficult to reflect stator branch open welding Fault

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