Date Code 20000421 Maintenance and Testing 7-33
SEL-251, -2, -3 Instruction Manual
of the drawout assembly. The power supply and transformer assembly are attached to the
bottom of the relay chassis.
The relay contains devices sensitive to Electrostatic Discharge
(ESD). When working on the relay with front or top cover removed,
work surfaces and personnel must be properly grounded or
equipment damage may result.
3. Disconnect the power supply and transformer secondary cables from the underside of the
drawout assembly.
4. Remove the drawout assembly by pulling the spacers on the bottom of the assembly. You
should be able to remove the assembly with your fingers. If the drawout assembly does not
come free, check to make sure all communications cables are disconnected from the relay rear
panel. Because steps 5 and 6 involve handling electrostatic discharge (ESD) sensitive devices
and assemblies, perform these steps at an ESD safe work station. This will help prevent
possible damage by ESD.
5. Note the orientation of the integrated circuit components to be replaced. Use an IC removal
tool or a small screwdriver to pry the indicated ICs free from their sockets be careful not to
bend the IC pins or damage adjacent components.
6. Carefully place the new ICs in the appropriate sockets. Check the orientation of the ICs,
ensuring each IC is in its corresponding socket. Look for IC pins that bent under or did not
enter a socket hole.
Verify proper orientation of the replaced ICs before reassembling
the relay. Energizing the relay with an IC reversed irrecoverably
damages the IC. If you mistakenly reenergize the relay with IC
reversed, do not place the relay in service using those ICs, even if
you correct the orientation.
7. Slide the drawout assembly into the relay chassis. Using your fingers, push the assembly in
until the front of the assembly is flush with the front of the relay chassis. Reconnect the
power supply and transformer secondary cables to the receivers on the underside of the
drawout assembly. Replace the relay front panel.
8. With breaker control disabled, turn relay power on and enter your settings. Execute the
STATUS, METER, and TRIGGER commands to ensure that all functions are operational.
Set and record your Access Level 1 and 2 passwords and the date and time. The relay is now
ready to resume protective functions.
9. If a new serial number label in included with the upgrade, attach the serial number label so
the old label is covered.
FACTORY ASSISTANCE
The employee-owners of Schweitzer Engineering Laboratories, Inc. are dedicated to making
electric power safer, more reliable, and more economical.
CAUTION
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CAUTION
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