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Phase-angle variance (Δθ) (see Figure 4.6-4)
The phase-angle variance of Vr and Vi (Δθ) is measured by the phase-angle variance-relay
having the setting [SyncRy1-Angle]. If the following equations are satisfied, the SyncRy1-
Angle relay determines that the phase-angle variance is inside the permissible range.
SyncRy1-Angle
Frequency-variance (Δf)
The frequency-variance of Vr and Vi (Δf) is measured by the frequency-variance relay having
the setting [SyncRy1-df]. If the following equations are satisfied, the SyncRy1-df relay
determines that the frequency-variance is inside the permissible range.
SyncRy1-df
where,
Frequency of Vr
Frequency of Vi
Δf Frequency-variance between Vr and Vi
Notice and tips
If the frequency-variance between the Vr and the Vi is shown very large, the SYNCHK may
fail to make the decision of the synchronism, although Off is set for the setting [SyncRy1-dfEN]
to abandon to checking the frequency-variance. This is because; the vector passes the [SyncR1-
Angle] zone very quickly. As a result, the SYNCHK relay may fail to issue the permission
command. To avoid the failure, the user has to set values for settings [SyncR1-Angle] and
[SYNC01_TSYN] depending on the assumed frequency-variance (Δf):
SyncR1-Angle
SYNC01_TSYN
where,
Δf= Frequency-variance (or cycle-slip in Hertz)
Tips: Cycles for the synchronism closure can be calculated:
Time length for getting a synchronism:
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