How does changing excitation affect parallel operation of alternators?

Changing the excitation of alternators in parallel operation primarily influences their ability to provide reactive power, which is critical for system stability and voltage regulation in a power system. When excitation levels are altered, the reactive power output of the alternators changes accordingly.

If one alternator is more or less excited than the others, it can lead to an imbalance in reactive power sharing among the units. In a parallel operation, each alternator is supposed to share the load effectively, which includes both active and reactive power components. If an alternator provides more reactive power due to higher excitation, it may draw less active load while another may end up supplying more active power but less reactive power.

This mismatch can lead to issues in voltage regulation; for instance, if you have alternators operating with differing excitation levels, the overall voltage stability can be compromised. Moreover, excessive reactive power provision can lead to increased losses and may even create system instability under certain conditions where the load requirements change rapidly.

Thus, while the answer indicates that changing excitation affects reactive power only, the scope of this impact also extends to overall system behavior, emphasizing the critical role reactive power plays in maintaining balance in a parallel operation of alternators.