I have encountered the 4.8 kV, 60 Hz system for the first time and I cannot see an overall advantage to it compared to a 4.16 kV system. Circuit breakers come in maximum voltages of 4.76 and 8.25 kV, so the later is needed. Since there is a 4.8 kV generator, it is not inconceivable that it could...
As gordonl touched on, important issues with large inertia are mechanical and materials. Starting by vfd is straight forward. First level software simulations are simple today -I personally have 8 different tools and the best one (brain) also.
In this case, the owner has the generator at one site which is downsized and would like to see if it can be used on another of their sites that is being expanded. Minimum cost is the first choice so I will try to reuse it at the lower voltage.
Is there a practical limit to a flywheel size in inertia, lb-ft^2 or kg-m^2 on a 500 HP, 480 V, 1800 rpm motor. I would like as big as I can have. For 60 Hz starting, the heat on starting will limit the size and that may be the value listed in Nema MG1. However, if started on a vfd it could be...
If I have an existing 600 volt, 3 phase, 60 Hz generator, approx 1500 kva, can I use it on a 480 volt system. The field current must be lower and the rating reduced to 1200 kva. Is this possible?
Thanks peterb. I also received a brochure on the CDG relay in pdf electronic format from Alstom which is very helpful. I started at their 24 hour contact centre:
www.tde.alstom.com/p-c/en/contcent.htm
Is there, on the internet, manuals for older electromechanical relay, GEC type CDG-23, in order to make the settings. Also, if approximate equations have been made, I would like to find them.