Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 545 / 706

13.3
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Testing and Troubleshooting
Testing Philosophy
At commissioning time, use the relay METER command to verify the ac
current and voltage magnitude and phase rotation. Use the PULSE command
to verify relay output contact operation. Use the TARGET command to verify
optoisolated input operation.
Maintenance Testing
When: At regularly scheduled intervals or when there is an indication of a
problem with the relay or system.
Goals:
1. Ensure that the relay is measuring ac quantities accurately.
2. Ensure that scheme logic and protection elements are
functioning correctly.
3. Ensure that auxiliary equipment is functioning correctly.
What to test: Anything not shown to have operated during an actual fault
within the past maintenance interval.
SEL relays use extensive self-testing capabilities and feature detailed metering
and event reporting functions that lower the utility dependence on routine
maintenance testing.
Use the SEL relay reporting functions as maintenance tools. Periodically
verify that the relay is making correct and accurate current and voltage
measurements by comparing the relay METER output to other meter readings
on that line. Review relay event reports in detail after each fault. Using the
event report current, voltage, and relay element data, you can determine that
the relay protection elements are operating properly. Using the event report
input and output data, you can determine that the relay is asserting outputs at
the correct instants and that auxiliary equipment is operating properly. At the
end of your maintenance interval, the only items that need testing are those
that have not operated during the maintenance interval.
The basis of this testing philosophy is simple: If the relay is correctly set and
connected, is measuring properly, and no self-test has failed, there is no reason
to test it further.
Each time a fault occurs the protection system is tested. Use event report data
to determine areas requiring attention. Slow breaker auxiliary contact
operations and increasing or varying breaker operating time can be detected
through detailed analysis of relay event reports.
Because SEL relays are microprocessor-based, their operating characteristics
do not change over time. Time-overcurrent operating times are affected only
by the relay settings and applied signals. It is not necessary to verify operating
characteristics as part of maintenance checks.
At SEL, we recommend that maintenance tests on SEL relays be limited under
the guidelines provided above. The time saved may be spent analyzing event
data and thoroughly testing those systems that require more attention.