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 frequency 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 frequency has exceeded the
Restore start Val
setting. The manual restoration includes a timer with the DT
characteristics. When the timer has reached the set value of the
Restore delay
time
setting, the RESTORE 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 resets 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.
4.5.2.5 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 that the
operating frequency remains approximately at the nominal frequency value by a small
1MRS758755 A Section 4
Protection functions
REC615 and RER615 447
Technical Manual
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