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750/760 Feeder Management Relay
GE Power Management
14.6 UNDERFREQUENCY RESTORATION 14 S7 CONTROL
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14.6 UNDERFREQUENCY RESTORATION 14.6.1 DESCRIPTION
This scheme is initiated by a trip of either the bus underfrequency 1 or 2 elements. After the feeder breaker has
been tripped, it will display message 'UFreq Restore Init' and operate any programmed output relays. Once ini-
tiated it will monitor the bus voltage level and frequency, and send a close command to the 2 CLOSE relay
when the voltage on the phase A input has risen above the programmed minimum level and frequency for a
selected time interval. The scheme is equipped with an incomplete sequence timer, so it will not remain initi-
ated for an indeterminate time, but will automatically reset if the voltage does not recover during the pro-
grammed interval. Initiation of the scheme can be canceled by a reset command. Cancellation of a previous
initiation is only effective if the voltage and frequency are above the restoration thresholds. A ‘Block Restora-
tion’ logic input is available to prevent both initiation and operation. It is recommended that if automatic under-
frequency restoration is to be used, that the cold load pickup feature is also enabled, to prevent the breaker
from tripping shortly after it is automatically closed.
14.6.2 SETPOINTS
■ UNDERFREQ RESTORE
■ [ENTER] for more
The Underfrequency Restoration setpoints path is:
\ SETPOINTS \ S7 CONTROL \ UNDERFREQ RESTORE
UNDERFREQ RESTORE
FUNCTION: Disabled
Range: Disabled, Alarm, Latched Alarm, Control
Select the required function.
UNDERFREQ RESTORE
RELAYS (3-7):
Range: Any Combination of the 3-7 AUXILIARY Relays
Select the output relays required.
UNDERFREQ RESTORE
MIN VOLTS: 0.90 x VT
Range: 0.00 to 1.25 in steps of 0.01 x VT
Enter the minimum value of voltage required to permit underfrequency restora-
tion to close the breaker.
UNDERFREQ RESTORE
MIN FREQ: 59.90 Hz
Range: 20.00 to 65.00 in steps of 0.01 Hz
Enter the minimum value of phase A bus frequency required to permit under-
frequency restoration to close the breaker.
UNDERFREQ RESTORE
DELAY: 10 s
Range: 0 to 10000 in steps of 1 s
Select the interval for which the voltage must remain above the minimum level
to permit underfrequency restoration to close the breaker.
INCOMPLETE SEQUENCE
TIME: 100 min
Range: 1 to 10000 in steps of 1 min
Select the interval during which the scheme will remain in operation after hav-
ing been initiated, after which the operation will be canceled.
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