Hello scheini111,
I assume there is no fault with aircraft (ie AC 1+2 are powered and B HYD is powered as well) prior to pressing any RAT sw:
1. If U press the RAT sw on the HYD panel: nothing will happen other than the extension of the RAT. In this case the RAT will not power the B sys because it is already powered.
2. If U press the RAT sw on the ELEC panel: Again the RAT will extend but it will do nothing. However, the EMER GEN will be powered and coupled to the network (powered by the already running B sys). Auto decoupling of EMER GEN occurs at L/G extension or during landing roll at low speed (depends on how old is the aircraft)
Thanks