
Protection
21
both side voltages of the circuit breaker for
synchronism conditions.
The synchronization function ensures the
stability of the network in three phase
reclosing condition. To do this, the two side
voltages of the circuit breaker are
compared in terms of magnitude, phase
angle
and
frequency
differences.
Additionally, closing can be done safely in
conditions that at least one side of the CB
has dead voltage.
Available
for
automatic
reclosing
(internally or externally)
Based on voltage/ angle/ frequency
difference
Synchro-check modes:
Synch-check
Energizing check, and synch-check if
energizing check failure
Override
Modes of energizing check:
Dead V
4
and dead V
3Ph
Dead V
4
and live V
3Ph
Live V
4
and dead V
3Ph
Synchro-check reference
voltage supervision
If the automatic reclosing is set for
synchronization check or energizing check,
during the automatic reclosing period, the
synchronization condition of the voltages
between both sides of CB cannot be met,
an alarm will be issued after default time
delay.
Auto-reclosing (79)
For restoration of the normal service after a
fault an auto reclosing attempt is mostly
made for overhead lines. Experiences
show that about 85% of faults have
transient nature and will disappear after an
auto reclosing attempt is performed. This
means that the line can be re-energized in
a short period. The reconnection is
accomplished after a dead time via the
automatic reclosing function. If the fault is
permanent or short circuit arc has not been
extinguished, the protection will re-trip the
breaker.
Main
features
of
the
Auto-reclosing are as follows:
Up to 4 shots (selectable)
Individually settable dead time for three
phase and single phase fault and for
each shot
Internal/external AR initiation
Three phase AR operation
CB status supervision
CB Aux. contact supervision
Cooperation with internal synch-check
function for reclosing command
Secondary system
supervision
Current transformer secondary
circuit supervision
Open or short circuited CT cores can
cause unwanted operation of some
protection functions such as earth fault
current and negative sequence current
functions.
Содержание CSC-161
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