2 Functions
144
7ST6 Manual
E50417-G1176-C251-A3
The device issues indications if, after a request to check synchronism, the conditions
for release are not fulfilled, i.e. if the absolute voltage difference
Max. Volt. Diff
,
the absolute frequency difference
Max. Freq. Diff
, or the absolute phase angle
difference
Max. Angle Diff
lie outside the permissible limit values. A precondition
for these indications is that voltages within the operating range of the relay are avail-
able. When a closing command is handled by the integrated control function and the
conditions for synchronism are not fulfilled, the command is cancelled, i.e. the control
function outputs „CO–“ (refer also to Section 2.19.1).
Operating Modes
The closing check procedure can be selected from the following operating modes:
SYNC-CHECK
=
Release at synchronism, that is, when the critical
values
Max. Volt. Diff
,
Max. Freq. Diff
and
Max. Angle Diff
lie within the set limits. This pa-
rameter is only displayed if you have checked the “Ad-
vanced Settings” checkbox in DIGSI.
Uref>Uline<
=
Release for energized busbar (URef>) and de-ener-
gized line (ULine<).
Uref<Uline>
=
Release for de-energized busbar (URef<) and ener-
gized line (ULine>).
Uref<Uline<
=
Release for de-energized busbar (URef<) and de-en-
ergized line (ULine<).
OVERRIDE
=
Release without any check.
Each of these conditions can be enabled or disabled individually; combinations are
also possible, e.g. release if
Uref>Uline<
or
Uref<Uline>
are fulfilled. Combina-
tion of
OVERRIDE
with other parameters is, of course, not reasonable.
The release conditions can be configured individually either for automatic reclosing or
for manual closing or for closing via control commands. You can, for example, allow
manual closing and control closing for synchronism or for de-energized feeder
whereas before an automatic reclosing operation, checking only de-energized condi-
tions at one feeder terminal and afterwards only synchronism at the other.
De-energized
Switching
For release of the closing command to energize a voltage free line from a live busbar,
the following conditions are checked:
• Is the feeder voltage ULine below the set value
Dead Volt. Thr.
?
• Is the reference voltage URef above the setting value
Live Volt. Thr.
but
below the maximum voltage
Umax
?
• Is the frequency fRef within the permitted operating range f
N
±
3 Hz?
After successful check the closing command is released.
Corresponding conditions apply when switching a live line onto a dead busbar or a
dead line onto a dead busbar.
Switching under
Synchronous
System Conditions
Before granting a release for closing under synchronous conditions, the following con-
ditions are checked:
• Is the reference voltage URef above the setting value
Live Volt. Thr.
but
below the maximum voltage
Umax
?
• Is the feeder voltage ULine above the setting value
Live Volt. Thr.
but below
the maximum voltage
Umax
?
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