Detection of field coil short-circuit fault in synchronous generators based on magnetic bypass shunt effect

The field coil short-circuit (FCSC) fault is a crucial factor that contributes to the severe vibration of the synchronous generators. The accurate detection of FCSC is of great significance as it facilitates a quicker confirmation and processing, and the key is to adopt a feasible real-time acquisition scheme for fault characteristics. According to the structural characteristics of the synchronous generator, we studied the magnetic bypass and shunt effect resulting from the structural components utilized to fix the stator core. A scheme of installing a magnetic flux detection coil on the back of the stator core of the synchronous generator was proposed. By analyzing the characteristic harmonics in the induced voltage of the detection coil, our proposed method is capable of detecting FCSC faults in the synchronous generator in real-time. A finite-element simulation model was established for a 334 MVA salient pole synchronous generator for method verification. The characteristic harmonic amplitudes of the induced voltages in the flux detection coil under different FCSC degrees were obtained. Also, several tests were conducted on a prototype synchronous generator with the type of MJF-30-6. The FCSC with varying fault degrees were simulated and the induced voltage signals of the flux detection coil were collected. Both simulation and test results validate our method in detecting the FCSC faults in synchronous generators. Additionally, our method also addresses the security concerns associated with sensor layout and offers a feasible solution for FCSC fault detection in synchronous generators.