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7-10
Maintenance and Testing
Date Code 20011026
SEL-321/321-1 Instruction Manual
T
ESTING
M
ETHODS AND
T
OOLS
Test Aids Provided by the Relay
The following features assist you during relay testing.
METER
Command
The
METER
command shows the voltages and currents presented to the
relay in primary values. The relay calculates Megawatts (MW) and
Megavars (MVAR) from these voltages and currents. These quantities are
useful for comparing relay calibration against other meters of known
accuracy.
Event
Reporting
The relay generates an 11-cycle event report in response to faults or
disturbances. Each event report contains voltage and current information,
relay element states, and input/output contact information in quarter-cycle or
sixteenth-cycle resolution. If you question the relay response or your test
method, use the event report for more information.
Each event report is date and time tagged relative to the triggering instant. If
the timeout of a protective element results in a TRIP, the relay records a
second event report. Thus, the relay may generate two event reports for a
long duration fault: the first when the instantaneous element asserted, the
second when the TRIP occurs.
Where Time Delayed Pickup (TDPU) timers are concerned, the time tag in
the event reports may be used to determine the validity of a TDPU timer
setting. Simply subtract the latest event report time tag from the previous
event report time tag.
Section 2: Specifications
has further details
concerning event report generation.
Programmable
Logic
Programmable logic allows you to test individual relay elements. See the
SET L command description in
Section 3: Communications
for further
details.
TARGET 44
Command
The
TARGET 44
command shows the state of the eight relay logic inputs in
a relay with one I/O board. This allows you to monitor the input states while
asserting the inputs to verify correct wiring and correct operation of the
inputs.
For more information on these commands, see
Section 3: Communications
.
Test Methods
There are two means of determining the pickup and dropout of relay elements: front panel LCD
indication and output contact closure.
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