The relay detects that a power swing is occurring and blocks operation of certain elements during that swing. During the swing the impedance could move through the instantaneous zone 1 and there could be reasons why tripping at that point could be undesirable. It could be a stable swing where there is no need to trip or it could be an unstable swing but it is desirable to trip elsewhere or at a different point in the swing. Waiting can result in reduced voltage across the opening contacts and thus a reduced likelihood of restrike.
I’ll see your silver lining and raise you two black clouds. - Protection Operations
What david said . . . but are you looking to understand how power swing and power swing blocking are applied, or under what circumstances to use them? I can't quite tell from your post.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
Thanks David for your response , how the timer settings are applied during the relay testing and importance of the same, I will read and try to understand.
