Thanks very much for the interesting and informative tutorial from
someone in the industry. I have one question:

Nick wrote:
. . .
Another possibly relevant story. We connect our emergency diesel
generator to the grid for testing and load it to about 3000 kW and
typically from 0 to 100 kVAR. But to fully test the excitation system,
the kVAR is at some point raised to 1400. . .

If your customers' loads were, for the sake of argument, purely
resistive as seen at your power plant output, then the voltage and
current would be in phase at that point. But in order to make your
generator produce "reactive power", the voltage and current have to be
forced out of phase at the generator. How is this resolved? Is that
reactive power "delivered" to (actually swapped back and forth between)
other generators in the system -- that is, do the other generators in
the system shift their own phase angles so that the V and I can be at
some angle other than zero at your generator output (and, necessarily,
also at the outputs at other generators in the system) yet in phase at
your customers' loads? Or do you have some local bank of reactance that
you can switch in to feed the "reactive power" back and forth to when
you run this test?

Roy Lewallen, W7EL