Abstract: In an electrical power generating installation which includes a plurality of turbine-generator sets, a parking bus is disclosed, which is provided with a potential regulated at a relatively low and constant frequency of the order of 1-2 Hz. Switching and phase and frequency matching means are provided, which enable the same controlled variable frequency starting system used for start-up of the turbine-generator sets, to be used for gradually adjusting the rotational speed of a selected turbine-generator set to a point where phase and frequency may be matched with that of the parking bus, to then permit the generator member of such set to be electrically transferred to the bus. By means of such arrangement, any number of turbine-generator sets may be connected in parallel to the parking bus which thereupon effects a simultaneous, continued low speed rotation of the sets for cooling or other purposes.