IN OLTC we observed "OUT OF STEP" Alarm, we have two
different transformer, when both are in parallel this type
of alarm observed. what's the meaning of this alarm and why
it occurs???

Answer Posted / nasseem

Out of step means that the Two transformers at different tap.
i.e. TR-1 at tap n and TR-2 at tap n+1 or n-1.
And as you know the two transformers should have same tap
"if the two transformers have same tap size i.e 1.25% for
example" when it operated in parallel to prevent the
circulation current between the two transformers.

So it seems in your case if we assume TR-1 is master and
TR-2 is follower TR-1 change its tap position while TR-2
still at it is original tap.

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