Following conditions are needed for generation synchronization :

1 Phase Sequence

2 Voltage Magnitude

3 Frequency

4 Phase Angle

I have question about Phase angle assuming that the frequency is the same and there is a big phase angle then the phase angle will never change. And I should wait for the phase angle to be minimal but there is a chance that this could never happen. What happen in practice?

  • 1
    \$\begingroup\$ I think you have to slow down or speed up the frequency of one of the generators by a very small amount until the phase angle is small enough. Not sure. I think it is rare for two generators to be so closely matched in frequency that the phase angle is constant. \$\endgroup\$
    – user57037
    Dec 31, 2020 at 9:11

1 Answer 1


If the frequency is in fact identical, then the phase angle will never change. However, this is not what is meant by that sequence of instructions, nor what happens in practice.

Getting the frequencies equal means nominal frequencies, getting it fairly close. With an unsynchronised generator, any slight change in drive power will alter the frequency slightly.

While the frequency is close, the phase will be changing slowly with respect to the grid. You observe the phase meter, and close the contactor when it's less than some specified tolerance.

If the phase is changing too fast, then the frequency is too far from the grid frequency. Adjust the frequency until the phase is changing slowly.

If the phase is wrong, and is not changing at all, then adjust the frequency until the phase is changing slowly.


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