J
Hello,
I've got a quick question about generator voltage control. First some background:
I operate a GE frame 7AE GTG coupled to a HRSG and associated STG in a COGEN plant. We generate power for use on-site but also for merchant power sales. Recently, we had to start a very large compressor motor. Our procedure is to have the utility tap up our transformer, raising the plant's 35kV bus voltage from 34.8kV to 35.6kV. We are also asked to move our GTG's MVARs from its usual amount (+11 MVAR) to -10MVAR. I didn't have to adjust this, as the MVARS dropped on their own as the bus voltage climbed.
When the compressor motor is started there is a momentary drop in bus voltage (-1500 volts) and the GTG MVARs according shoot up from -10 MVAR to +33 MVARs.
My question is, why does the GTG MVAR output drop when the bus voltage is raised by the utility? Shouldn't the exciter increase the current flow and try to maintain the original MVAR output? Our Alstom STG has a physical setpoint for generator terminal voltage (13.8kV) but I don't see anywhere on the Mark VIe to input a generator terminal voltage for the GTG... all I've got are raise and lower buttons that seem to bump the VARS up or down by about 2.5MVAR per click.
If anyone can shed some light on the excitation control for the GTG it would be greatly appreciated.
Thanks!
Jeff
I've got a quick question about generator voltage control. First some background:
I operate a GE frame 7AE GTG coupled to a HRSG and associated STG in a COGEN plant. We generate power for use on-site but also for merchant power sales. Recently, we had to start a very large compressor motor. Our procedure is to have the utility tap up our transformer, raising the plant's 35kV bus voltage from 34.8kV to 35.6kV. We are also asked to move our GTG's MVARs from its usual amount (+11 MVAR) to -10MVAR. I didn't have to adjust this, as the MVARS dropped on their own as the bus voltage climbed.
When the compressor motor is started there is a momentary drop in bus voltage (-1500 volts) and the GTG MVARs according shoot up from -10 MVAR to +33 MVARs.
My question is, why does the GTG MVAR output drop when the bus voltage is raised by the utility? Shouldn't the exciter increase the current flow and try to maintain the original MVAR output? Our Alstom STG has a physical setpoint for generator terminal voltage (13.8kV) but I don't see anywhere on the Mark VIe to input a generator terminal voltage for the GTG... all I've got are raise and lower buttons that seem to bump the VARS up or down by about 2.5MVAR per click.
If anyone can shed some light on the excitation control for the GTG it would be greatly appreciated.
Thanks!
Jeff