Date Code 20020129
Testing and Troubleshooting
10-43
SEL-387E Instruction Manual
Use the SEL-387E Relay Commissioning Test Worksheet, located at the end of this section, to
verify correct CT connections and settings when placing the relay in service. The worksheet
shows how using software commands or the front-panel display can replace the need for the
traditional phase angle meter and ammeter.
M
AINTENANCE
T
ESTING
When:
At regularly scheduled intervals, or when there is an indication of a problem with the
relay or system.
Goals:
a)
Ensure that the relay is measuring ac quantities accurately.
b) Ensure that scheme logic and protection elements are functioning correctly.
c)
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 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 and current differential element 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.
