Technical description
2 Protection functions
2.10 Synchrocheck (25)
VM55.EN005
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2.10.
Synchrocheck (25)
VS_Sync VS_Scaling Enable_Sync
Synchrocheck is a function that will check synchronism in both
sides of the opened circuit breaker. The function will monitor
voltage amplitude, frequency and phase angle difference
between two voltages. The reference for synchrocheck can be
phase to ground or phase to phase voltage.
Voltage measuring mode must be selected to enable
synchrocheck from the desired reference. Available voltage
modes are 3LN/LLy for phase to phase voltage reference and
3LN/LNy for phase to ground reference.
The voltage used for sychrochecking is always phase-to-phase
voltage U
12
or phase to ground voltage U
1
Setting parameters of synchrocheck stage SyC1 (25):
Parameter Values
Unit
Default
Description
Side
U12/U12y;
-
U12/U12z
Voltage selection. The
stage 1 has fixed voltages
U12/U12y or U12/U1y
CBObj
Obj1
-
Obj1
The selected object for CB
control. The synchrocheck
closing command will use
the closing command of
the selected object.
NOTE!
The stage 1 is
always using the object 1.
Smode
Async;
Sync; Off
-
Sync
Synchrocheck mode.
Off = only voltage check
Async = the function
checks dU, df and dangle.
Furthermore, the
frequency slip, df,
determines the remaining
time for closing. This time
must be longer than “CB
time”.
Sync mode =
Synchronization is tried to
make exactly when angle
difference is zero. In this
mode df-setting should be
enough small (<0.3Hz).