Negative sequence impedance direction protection method for interior failures of stator winding of steamer generator

Abstract

The invention relates to a protection method for interior failures of a stator winding of a steam turbine generator, belonging to the technical field of main equipment relay protection of a power system. The protection method is characterized by comprising the following steps of: collecting three-phase voltage and three-phase current from the machine end of the generator, filtering fundamental wave negative sequence components of failure components of phase voltage and phase current, calculating the equivalence negative sequence impedance of the failure components of the machine end, and judging whether unsymmetrical failures are interior failures of a motor winding or exterior failures of the machine end according to the symbol and the size of the negative sequence impedance. Analysis for the calculation of all interior short-circuit failures and single-branch welding disconnection failures which possibly occur and the sensitivity in two typical steam turbine generators shows that the negative sequence impedance direction protection method for failure components has superior sensitivity and protection range for the interior asymmetrical failure (particularly a short-circuit failure among interior turns) of the rotor winding of the steam turbine generator to the other traditional protections, and can provide high-quality protection for interior asymmetrical failures of the steam turbine generator, the natural point side of which only leads out three terminals.

Description

technical field [0001] The invention belongs to the technical field of relay protection for main equipment in a power system, and in particular relates to a method for protecting an asymmetric fault inside a generator stator winding based on the sign and magnitude of the fault component negative-sequence impedance. Background technique [0002] The internal asymmetrical faults of the generator stator mainly include the internal short-circuit faults of the windings and the single-branch disconnection faults, which are common and highly destructive faults. Large turbo-generator internal short-circuit faults will generate a large short-circuit current, while single-branch disconnection faults not only cause the normal branch current of the fault phase to increase significantly, but also generate a large current between the two branches of the non-fault phase. Circulating current, such a large current may burn the winding and iron core, and also generate destructive and serious ...

AI Technical Summary

Problems solved by technology

[0003] However, most of the existing turbogenerators have only 3 terminals on the neutral point side (see figure 1 ), it is impossible to configure zero-sequence current type transverse difference protection, incomplete longitudinal difference protection and split-phase transverse difference protection, etc., which are commonly used in the turn-to-turn short-circuit main protection of hydro-generators, while the complete longitudinal difference protection with installation conditions can only respond to the stator winding phase-to-phase short circuit, it cannot act on the internal turn-to-turn short circuit and single branch disconnection fault of the stator winding

[0004] Turn-to-turn short-circuit protection for turbogenerators currently in use mainly includes longitudinal fundamental wave zero-sequence overvoltage protection and fault component negative-sequence direction protection, but both have relatively large action dead zones, and the latter generally cannot respond to single-branch disconnection Fault

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