Key:generator:plant

In some complex power generation systems, several generators can be chain together to produce output power of a given power plant. It's useful to distinguish ones which produce intermediate power from those which effectively produce the output of the power plant.

• generator:plant=intermediate generators are converting power from source to an intermediate form.
• generator:plant=output generators are using intermediate power to produce the power plant output.

It's optional

This distinguishing is actually optional. Mappers don't have to (but they are invited to) map intermediate generators since no consistency check may be done on them. The whole power plant output rating only depends on generator:plant=output generators which are the most common ones and pretty always exposed in public documentation.