Page 786 - Basic Electrical Engineering

frequency of the busbar voltage.
iii. The phase sequence of the voltages of the incoming generator should be the same as the phase
sequence of busbar voltages.

It may be noted that the kVA or MVA rating of the alternators connected in

parallel need not be the same.
Synchronization of alternators is done using a synchroscope or

synchronizing lamps to make sure that the conditions of parallel operation are
met.
Once an alternator is synchronized, it gets connected to the busbar. Now it

has to share a portion of the common load. This is called load sharing. If load
sharing is not done, the generator will simply remain connected to the busbar;

this condition is called floating of the generator with the busbar.
After synchronization, two things can be changed: the excitation of the

generator or its prime-mover input.
We will study the effect of change of excitation and that of the prime-

mover input on load sharing by an alternator.

10.14.4 Load Sharing

Let the incoming generator G be connected to the busbar where one
2
generator G is already connected. See Fig. 10.16. After synchronization, G 2
1
will simply float on the busbar. It will neither draw any current nor supply
any current. For load sharing by the incoming alternator two things can be
done. We can change the field current (excitation) or we can change the input

to the prime mover driving the generator.