ABB RELION 620 Series Technical Manual page 339

1MAC504801-IB E
620 series ANSI
Technical Manual
Restoring mode Description
Disabled Load restoration is disabled.
Auto In the "Auto" mode, input frequency is continuously compared to the
pickup 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
setting, the RESTORE output is activated if the restoring condition still persists. If the
frequency drops below the
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
setting. The manual restoration includes a timer with the DT characteristics. When
the timer has reached the set value of the
output is activated if the restoring condition still persists. If the frequency drops
below the
reset timer is activated. If the reset timer reaches the value of the
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 TRIP output, that is, when the next load-
shedding operation is detected.
If there is a sharp frequency change in the waveform it can result in a
prolonged operate time. The reason is that the frequency algorithm does
not see it as a change in frequency, but as a loss of mains situation. In this
case frequency protection is delayed with 160 ms to give room for vector
shift protection to operate.
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
trip timer is frozen to the prevailing value, but the TRIP output is not deactivated when
Restore pickup Val before the RESTORE output is
Restore pickup Val setting before the RESTORE output is activated, the
Section 4
Protection functions
Restore
Restore delay time
Restore pickup Val
Restore delay time setting, the RESTORE
Reset delay time
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