Modelling individual and lumped generators

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I have two generators, say 50 MVA each and having 0.18 reactance, connected to a bus. If I lump them together as one machine, what changes do I need to make in the parameters?

Also:

1. What would be the new reactance in the lumped condition? What will be the changes in Qmax and Qmin, considering the fact the two machines had same reactive power capability curves?

2. Will the generator model, for example GENROU, have any changes in the parameters for the lumped machine?

3. From the stability point of view, what major differences will there be between two individual machines and one single lumped machine?

Thank you in advance.