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Section 4
1MAC050144-MB C
Protection functions
274
615 series ANSI
Technical Manual
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.
Blocking logic
There are three operation modes in the blocking functionality. The operation modes are
controlled by the
BLOCK
input and the Configuration > System > Blocking mode global
setting 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 IED 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. In the "Block all" mode, the whole function is
blocked and the timers are reset. In the
"Block TRIP
output" mode, the function
operates normally but the
TRIP, OPR_FRQ
and
OPR_FRG
outputs are not activated.
4.3.2.5
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
margin. The safe margin of operation is usually less than ±0.5 Hz. The system frequency
stability is one of the main concerns in the transmission and distribution network operation
and control. To protect the frequency-sensitive electrical equipment in the network,
departure from the allowed band for safe operation should be inhibited.
Restoring mode Description
Disabled
Load restoration is disabled.
Auto
In the "Auto"? mode, input frequency is continuously compared to the
Restore 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
Restore delay time
setting, the RESTORE
output is activated if the restoring condition still persists. If the frequency drops below
the Restore pickup 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 pickup 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 pickup 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..
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Страница 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
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Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
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