When the generator is running low, its efficiency and that of the running machine decrease, so we can choose the parallel operation of the generators. For this operation we must observe:

– that the generator voltage is identical to the mains voltage;

– that the phase angle of the voltage caused by the generator must satisfy that of the grid;

– that the frequencies of the systems must be almost equal;

– The order of the phase sequence at the points to be connected must be identical.         gamasco

When we apply the load to the generator we will suddenly have a voltage drop on its terminals, and that fall will depend on the generator reactance, the current, the load power factor and the type of regulation. The biggest problems with this fall happen at the start of induction electric motors.

The protection of the generator with voltage regulation independent of the frequency, connected with rotations below 90% of its nominal rotation, during a long period, must be turned off. If the generator feeds into a mains supply and a short circuit occurs in the mains, and after the short if the mains voltage drops to 50% of the rated value, the generator must be disconnected from the mains immediately.