Over Frequency Threshold
This is the frequency (in hertz) above which a Trip operation will occur. Enter between
50 and 62 Hz, but the setting will be valid only if it falls within the range (System Frequency,
System Frequency + 2). (Minimum: System Frequency; Maximum: System Frequency
+ 2 Hz; Default: System Frequency + 0.5 Hz; Increment: 0.02)
Frequency Time to Trip
This is the time (in seconds) the underfrequency or overfrequency threshold must be
exceeded for a Trip operation to occur. (Range: 0.06-600.00; Step: 0.02; Default: 30.00)
Reset Time
This is the time (in seconds) good frequency must be present for the Frequency element
to reset. (Range: 0.06-600.00; Step: 0.02; Default: 1.00)
Low Frequency Indication (IntelliTeam SG System and Loop Restoration Only)
The Low-Frequency Indication mode detects an underfrequency event immediately
before loss of voltage so the loop-restoration system or the IntelliTeam SG Automatic
Restoration System can be taken out of the Ready state to prevent automatic load pick
up during an underfrequency load-shedding event.
This feature should be coordinated with the underfrequency-detection scheme that
will result in the load-shedding operation. The Under Minimum Time Detect setpoint
must be faster than the underfrequency-detection scheme to ensure the low frequency
indication will prohibit restoration before an underfrequency load-shed event. Similarly,
if the IntelliRupter fault interrupter’s Under Frequency Trip element is used to open
the device with IntelliTeam SG restoration software, the Under Minimum Time Detect
setpoint must be faster than the Frequency Time to Trip setpoint to ensure restora-
tion is prohibited before the Trip operation. The Under Frequency Trip element will
not disable the Loop Restoration mode or IntelliTeam SG system-restoration features
when it trips open the IntelliRupter fault interrupter.
Loop Restoration: When the Good Frequency to Close setting for the profile
designated on the Setup>Restoration>Loop screen is set to the Yes state and the Under
Frequency Enabled setpoint is also set to the Yes state, a Loop Restoration Close
command will be blocked if the frequency is below the active Under Frequency
Threshold setpoint for the configured Under Frequency Minimum Time to Detect
setpoint. Loop restoration must be manually enabled after the low-frequency condition
has cleared. (The Under Frequency Threshold default value = System Frequency –
0.5 Hz, 49.50 Hz when Setup>General>Site-Related>System Frequency = 50 Hz or
59.50 Hz when Setup>General>Site-Related>System Frequency = 60 Hz; Minimum:
System Frequency – 3 Hz; Maximum: System Frequency; Increment: 0.01 Hz) Configure
the Under Frequency Minimum Time to Detect setpoint. (Range:0.10-10.0; Step: 0.02)
IntelliTeam SG System: When the Under Frequency Enabled setpoint is set to
the Yes state and the Under Frequency Threshold setpoint identifies an underfre-
quency load-shed event (the underfrequency is at or below the active Under Frequency
Threshold setpoint for the duration of the Under Frequency Minimum Time to
Detect Timer), it sets the IntelliTeam SG system to the Prohibit Restoration mode,
and the IntelliRupter fault interrupter goes out of the Ready state at that location. When
an IntelliRupter fault interrupter is not in the Ready state, restoration must be manually
enabled to return the IntelliTeam SG system to the Normal state.
84 S&C Instruction Sheet 766-530
Protection Setup
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