2-40 Specifications Date Code 20011026
SEL-321/321-1 Instruction Manual
Active Groups and Group Variables
The relay only uses one group setting at a time. The other setting groups are stored in
nonvolatile memory.
The setting group used at any one time is called the Active Group. Contact inputs control the
Active Group selection. The setting group selected by the GROUP command is labeled Group
Variable. If the inputs select Group Variable, the GROUP command controls the setting group
selection.
Global Settings
Inputs SS1 - SS3 Assign to any input. Assignment order is not important.
Timed Group Reset TGR Minimum delay that inputs (or input) selecting a new
setting group must be asserted before group is switched.
METERING
Units: Primary, computed from secondary inputs times instrument transformer ratio
settings.
Accuracy: ±1.0% of nominal input at rated voltage and current.
SYSTEM FREQUENCY TRACKING
The relay adjusts its sampling rate by monitoring the system frequency using a zero-crossing
detector on the A-phase voltage input. The relay can be ordered with a nominal frequency of
either 60 or 50 Hz.
The frequency tracking range is 55 to 65 Hz for 60 Hz relays and 45 to 55 Hz for 50 Hz relays.
When the relay is first powered on, it assumes the nominal frequency.
Accuracy: ±0.028 Hz at 60 Hz
±0.020 Hz at 50 Hz
FAULT LOCATOR
Fault locations are computed from data stored in the event report.
Select the fault locating method in the relay settings: set LOCAT = Y when there are current
sources in front of the relay location, and set LOCAT = R for radial applications. Set LOCAT =
N to disable the fault location feature.
One of the elements in Table 2.26 must assert in the event report data for the relay to calculate a
fault location.
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