Analysis of Basic Working Principles of Generator Differential Protection
The internal short-circuit fault of the generator is mainly the phase-to-phase and inter-turn short-circuit fault of the specified sub-winding. When the short-circuit fault occurs, a large inrush current will be formed, and the generated strong arc will burn the stator winding insulation and may cause a large fire. Even the generator is scrapped, the consequences are very serious. Therefore, it is required to install the generator differential differential protection as the main protection for the stator winding and the inter-turn short-circuit fault of the generator, and the action is to disengage the generator.
1. The role of longitudinal differential protection
The phase-to-phase short circuit of the stator winding of the reaction generator and its lead-out line is the main protection of the generator.
2. Basic schematic diagram of longitudinal differential protection
Compare the magnitude and phase of the current across the generator, which is the phase-to-phase fault that reflects the generator and its lead-out. The two side current transformers of the generator longitudinal differential protection have the same ratio and the same type.
Ratio brake type differential protection works
The operating current of the proportional braking type differential protection is changing. It automatically changes with the change of the short-circuit current, ensuring that the external short-circuit fault is not erroneous and has high sensitivity to the internal short-circuit fault.
Taking the generator one phase as an example, it is stipulated that the primary current flows into the generator in the positive direction. When running normally and sending
When a fault occurs outside the protected area, the differential current flowing into the differential relay is zero, and the differential relay will not operate. When an internal fault occurs in the generator, the differential current flowing into the differential relay will have a large value. When the differential current exceeds the set value, the differential relay is judged to have an internal fault of the generator and acts on the de-listing power generation. machine.