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
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