What is a typical power rating (MVA) of a transformer which connects a synchronous generator to the MV grid? I would think that there is just a safety margin compared to the rating of a generator, for example, 10% more. Therefore, to connect a generator of 90 MVA I would install a transformer of 100 MVA. But I don't know if this is correct. Do you know which are the typical values of it?

  • \$\begingroup\$ If you are an amateur, then who cares exactly what the ratings mean. If you are a professional, then you are asking in seriously the wrong place. For your location, get a copy of the local electricity supply regulations, and read them. Your employer will not be happy if you specify the wrong size transformer. Too big is too costly. Too small and your insurance doesn't cover you when it goes bang, which is even more costly. \$\endgroup\$
    – Neil_UK
    May 14 at 9:06
  • \$\begingroup\$ @Neil_UK I am an amateur, I ask it just for curiosity. I care about it otherwise I would not have asked here. I like to know typical values of some quantities in the electric grid, it could help in my future career \$\endgroup\$ May 14 at 9:21
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    \$\begingroup\$ At the 100 MVA level, it's a whole different ballgame to house wiring. Short circuit currents cause large Lorentz forces, ripping conductors out of their moorings, so need controlling by having a minimum impedance in the circuit. Transformers are sized so that the temperature stays low enough so that the insulation takes 100 years rather than 10 years to degrade, controlling rate of capital outlay on replacing equipment. Generators, transformers and transmission lines are sized for N+1 redundancy so that one can be in maintenance at any time. Commercial considerations rule. \$\endgroup\$
    – Neil_UK
    May 14 at 10:27


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