Online Monitoring of Inter-turn Short Circuit Fault of Field Winding in Large Turbo-generator

A field winding inter-turn short circuit is commonly encountered in the normal operation of a turbo-generator. When an inter-turn short circuit occurs, a large amount of higher harmonics will appear in the voltage of the generator, endangering the safe and stable operation of the generator. To identify an inter-turn short circuit, a tiny coil mounted in the air gap is commonly used. However, the performance of the tiny coil will depend heavily on the location of the coil. Moreover, the characteristics of the air-gap magnetic fields will be different for different inter-short circuit faults. In this respect, a methodology to investigate the influence of the location of the tiny coil and the characteristics of the air-gap magnetic field in different short-circuit conditions is proposed and numerically validated.