U.6.2
SEL-421 Relay User’s Guide Date Code 20090715
Testing and Troubleshooting
Testing Philosophy
Commissioning
Testing
SEL performs a complete functional check and calibration of each SEL-421
before shipment so that your relay operates correctly and accurately. You
should perform commissioning tests to verify proper connection of the relay
to the power system and all auxiliary equipment. Check control signal inputs
and outputs. Check breaker auxiliary inputs, SCADA control inputs, and
monitoring outputs. Use an ac connection test to verify that the relay current
and voltage inputs are the proper magnitude and phase rotation.
Brief fault tests confirm that the relay settings and protection scheme logic are
correct. You do not need to test every relay element, timer, and function in
these tests.
At commissioning, use the relay METER command to verify the ac current
and voltage magnitude and phase rotation (see Examining Metering
Quantities on page U.4.33).
Use the PUL command to pulse relay control output operation. Use the TAR
command to view relay targets and verify that control inputs are operational.
Use TEST FM, TEST DNP, and TEST DB to check SCADA interfaces. (See
TEST DB on page R.9.52 for information on these relay commands.)
Table 6.2 lists guidelines for commissioning testing. For further discussion of
these tests, see Checking Relay Operation on page U.6.24.
Maintenance Testing
The SEL-421 uses extensive self-testing routines and features detailed
metering and event reporting functions. These features reduce your
dependence on routine maintenance testing. When you want to perform
maintenance testing, follow the recommendations in Table 6.3.
Table 6.1 Acceptance Testing
Details Description
Time Test when qualifying a relay model for use on the utility system.
Goals a) Confirm that the relay meets published critical performance specifications
such as operating speed and element accuracy.
b) Confirm that the relay meets the requirements of the intended application.
c) Gain familiarity with relay settings and capabilities.
Test Test all protection elements and logic functions critical to your intended
application.
Table 6.2 Commissioning Testing
Details Description
Time Test when installing a new protection system.
Goals a) Validate all system ac and dc connections.
b) Confirm that the relay functions as intended using your settings.
c) Check that all auxiliary equipment operates as intended.
d) Check SCADA interface.
Tests Test all connected/monitored inputs and outputs, and the polarity and phase
rotation of ac connections. Make simple checks of protection elements. Test
communications interfaces.
Courtesy of NationalSwitchgear.com
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