Asynchronous Operation of a Synchronous Generator Following a Fast Loss of Field Detection: Challenges and A Remedy

Asynchronous operation of a synchronous generator (SG) following a loss of field (LOF) incident can lead to potential mechanical damages, as well as overheating in the stator winding, rotor body and stator end core region. To protect SGs from being damaged, power plant protection codes recommend prompt LOF detection and tripping of SGs. This study first demonstrates that the severity of above consequences after LOF events is directly affected by the SG’s initial loading. A remedial action (RA) through the generation output reduction after a fast LOF detection is then explored to achieve two objectives: 1) to prevent the SG from entering a hazardous state, and 2) to allow time for either restoring the excitation system or executing a controlled shutdown of the SG. LOF detection can be performed using a fast existing scheme that triggers the RA. The simulated case studies demonstrate that the proposed RA enables safe asynchronous operations of the SG after a LOF incident, and also provides an opportunity to either restore the SG’s excitation system or initiate a planned outage.