KLINGERMAN
Electrical
- Jul 19, 2010
- 2
I have a generator connected to the grid using a delta-wye transformer. The generator is a 12MVA machine, and runs at 4.16KV. Recently, while it was operating, the C phase opened, however it took longer than we would have expected for the negative sequence relay to operate. I am familiar with symmetrical components, but not with "single phasing". I have done a lot of research, and I think I am now just more confused than ever before. I know the FLA for each phase before the C phase of the breaker opened was 1665amps. I also know that since it was connected to the grid, the voltages would have been unaffected by this event, and lastly I know the two remaining currents would have shifted to 180° apart.
I guess most of my confusion is coming from most of the things I have read say the currents would have behaved similarly to a Ph-Ph fault (.8667 at 180° apart) however, I also know that there was still 12 MW worth of water (a hydro unit) flowing through this machine. Some of this power was consumed in the form of heat, but I have a hard time believe the entire 4MW of power that were on the C phase was consumed as extra heat inside of the machine.
I have gone in a few circles with this question, I hope it is clear what I am asking. I can provide a drawing if necessary.
Thank you.
I guess most of my confusion is coming from most of the things I have read say the currents would have behaved similarly to a Ph-Ph fault (.8667 at 180° apart) however, I also know that there was still 12 MW worth of water (a hydro unit) flowing through this machine. Some of this power was consumed in the form of heat, but I have a hard time believe the entire 4MW of power that were on the C phase was consumed as extra heat inside of the machine.
I have gone in a few circles with this question, I hope it is clear what I am asking. I can provide a drawing if necessary.
Thank you.