"I've gots lots of experience with LTC's, but almost none with generation, so I'm looking at this from the utilities side rather than the generators side.
Which is another way of saying I'm confused!
"Are you essentially over exciting the generator to go leading? If so, isn't this done within the generator, and not with the LTC?
Or am I missing this altogether?"
Don't feel bad, because it's hard for me to understand sometimes too. In effect what we have is something almost abstract that almost know one here (power plant) knows anything about. I think if I knew any less, I'd be completely confused about it.
I think though that the situation here is an exception to what is the norm. The reason is, there are two generators in isochronous generation, but we are importing electricity, and not exporting it. Therefore VARS are a concern, which is another way of saying PF is a concern.
To control the VARS, we use the tap changer on VAR control which changes voltage up or down to send VARS back to us.
I wish I could explain the cooperation between the automatic operation of the voltage regulator of the generator and the automatic control of the LTC, but that's the one area I need to figure out.
I can say that aside from manually moving the LTC to change voltage, we would use the generators voltage regulator to over-excite the gen to bring voltage up which usually happens immediately. To lower voltage, we drive down the voltage regulator, or under-excite it to export VARS to the city, thus causing the VARS regulator to exceed setpoint, causing the LTC to tap to lower voltage, which moves VARS back to our generator.
I'm pretty rusty on the lead vs. lagging PF in how it works.
I wish I could explain this better, but in the end the LTC is in VARS regulate, not voltage regulate.
Maybe someone more freshly familiar with this can explain it better. My understanding is probably rudimentary based on the actual effects of the operation rather than the proper fundamentals electrically.
I have heard it said that the purpose of VAR regulating with the LTC is so that the city utility maintains a leading PF.
[This message has been edited by rat4spd (edited 09-19-2005).]
