Restoring mode
Description
Disabled
Load restoration is disabled.
Auto
In the “Auto” mode, input frequency is continuously compared to the
Restore start Val
setting. The restore detection module includes a
timer with the DT characteristics. Upon detection of restoring, the
operation timer activates the
ST_REST
output. When the timer has
reached the value of the
Restore delay time
setting, the
RESTORE
output is activated if the restoring condition still persists. If the fre-
quency drops below the
Restore start Val
before the
RESTORE
output
is activated, the reset timer is activated. If the reset timer reaches
the value of the
Reset delay time
setting, the timer resets and the
ST_REST
start output is deactivated.
Manual
In the “Manual” mode, a manual restoration is possible through the
MAN_RESTORE
input or via communication. The
ST_REST
output
is activated if the
MAN_RESTORE
command is available and the fre-
quency has exceeded the
Restore start Val
setting. The manual resto-
ration includes a timer with the DT characteristics. When the timer
has reached the set value of the
Restore delay time
setting, the
RE-
STORE
output is activated if the restoring condition still persists. If
the frequency drops below the
Restore start Val
setting before the
RESTORE
output is activated, the reset timer is activated. If the reset
timer reaches the value of the
Reset delay time
setting, the timer re-
sets and the
ST_REST
start output is deactivated.
A condition can arise where the restoring operation needs to be canceled.
Activating the
BLK_REST
input for the "Auto" or "Manual" modes cancels the
restoring operation. In the "Manual" restoring mode, the cancellation happens even
if
MAN_RESTORE
is present.
Once the
RESTORE
output command is cancelled, the reactivation of
RESTORE
is
possible only after the reactivation of the
OPERATE
output, that is, when the next
load-shedding operation is detected.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the
BLOCK
input and the global setting in Configuration > System >
Blocking mode that selects the blocking mode. The
BLOCK
input can be controlled
with a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the
BLOCK
input signal activation is
preselected with the
Blocking mode global setting.
The
Blocking mode setting has three blocking methods. In the "Freeze timers"
mode, the operate timer is frozen to the prevailing value, but the
OPERATE
output
is not deactivated when blocking is activated. In the "Block all" mode, the whole
function is blocked and the timers are reset. In the "Block OPERATE output" mode,
the function operates normally but the
OPERATE
,
OPR_FRQ
and
OPR_FRG
outputs are
not activated.
4.6.2.5
Application
An AC power system operates at a defined rated frequency. The nominal frequency
in most systems in the world is 50 Hz or 60 Hz. The system operation is such
Protection functions
1MRS757644 H
714
620 series
Technical Manual
