Paul Martin, a chemical engineer on Linkedin, has published some good work on economies of scale:
Chris Bright writes:
There are certain fixed overheads regardless of size. For example a tachometer for measuring the speed of a turbine generator.
Most turbo-generators are 2-pole and run at 3000 rpm on 50 Hz systems and 3600 rpm on 60 Hz systems.
For turbo-generators between 50 to 1000 MW there would not be much difference between tachometers and perhaps the same design could be used for any rating.
So if we decide to choose between suppling 1000 MW with one 1000 MW turbo-generators we would only need one tachometer, but if we chose 20 off 50 MW generators, we would need twenty tachometers.
Tachometers are a very small part of the overall costs, but similar principles apply to control, instrumentation and protection.
For example an ammeter to measure the current output of a generator. For all but the smallest generators, an ammeter does not measure the current directly, but via a current transformer (CT) instead. The CT is clamped around the generator output and currents of perhaps thousands of amps are transformed down to much smaller currents typically between 0 and 1 and the meter is scaled accordingly.
Similarly for many other measurements.
Likewise telemetry and control. The telemetry signals from a 500 MW turbo-generator would not be ten times as much data from a 50 MW one. Likewise the signal to operate a circuit breaker is much the same regardless of the rating of the circuit breaker.