Monitoring of inter-turn short circuit of rotor windings in synchronous generators without stator branch current transformer

The inter-turn short circuit of rotor windings is a normal electrical fault of a large turbine generator, and fault worsening will seriously hinder normal and safe operation of a generator. Since most of turbine generators in China are provided with no installation condition for a branch current transformer, application of the monitoring principle based on the stator unbalanced current RMS is limited. For solving the above problem, the paper provides a monitoring method of inter-turn short circuit of rotor windings in synchronous generators without stator branch current transformer. A fault monitoring criterion is formed according to change of excitation MMF before and after faults. In the calculation of real excitation MMF, only stator leakage reactance and no load characteristic curve of the generator are used, and influence upon calculation precision by the generator operating mode is smaller. Effectiveness of the monitoring method is verified through the experiment on a 12kW non-salient-pole synchronous generator with one pole. The method is also suitable for rotor two-point grounding fault protection.