7-58 Maintenance and Testing Date Code 20011026
SEL-321/321-1 Instruction Manual
Step 3. Remove the relay front panel by unscrewing the five front-panel screws. Carefully
lift the front panel up and out and then disconnect the front-panel communications
cables (P8 FP and P9 INTERFACE BUS) from the relay main board. With the front
panel removed, you can see the aluminum drawout trays. The main board is attached
to the top drawout tray. The power supply and transformer assembly are attached to
the bottom of the relay chassis. The relay interface circuit board trays lie between
the main board drawout assembly (above), and the power supply and input
transformers (below).
Step 4. Disconnect P12 PWR SUPPLY and P13 SIGNAL INPUTS from the front of the
main board drawout assembly.
Step 5. Remove the main board drawout assembly (upper tray) by pulling the nylon
extractors on the front corners of the drawout tray. (Be careful not to subject cable
assemblies to unusual mechanical stress or strain as the drawout assembly may snag
the cable assemblies upon drawout removal or replacement.) You should be able to
remove the assembly with your fingers. Because Steps 6 and 7 involve handling
devices and assemblies sensitive to ESD, perform these steps at an ESD-safe
workstation. This will help prevent possible damage by ESD.
Step 6. Note the orientation of the ICs to be replaced. (The orientation mark is typically a
half-circle indentation in one end of the IC.) Use an IC removal tool or a small
screwdriver to pry the indicated ICs from their sockets, being careful not to bend the
IC pins or damage adjacent components.
Step 7. Carefully place the new ICs in the appropriate sockets. Check the orientation of the
ICs. Be sure that each IC is in its corresponding socket. Look for IC pins that are
bent under or did not enter a socket hole.
CAUTION
!
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 an IC reversed, do
not place the relay in service using those ICs, even if you correct the
orientation.
Step 8. Slide the drawout assembly into the relay chassis. Using your fingers, push the
assembly in until it seats properly and the extractor levers are at their home
positions. Reconnect P12 PWR SUPPLY and P13 SIGNAL INPUTS cables to the
receivers on the front of the drawout assembly. Reconnect the P8 FP and P9
INTERFACE BUS cables leading from the front panel to the relay main board.
Replace the relay front panel.
Step 9. With breaker control disabled, turn relay power on. If the relay front panel displays
an INVALID message (i.e., GRP SET INVALID), Group and Global settings will
need to be verified. Connect a computer or terminal set to 2400 baud, 8 data bits, 1
stop bit to a relay serial communications port and enter Access Level 2. Execute the
SHOWSET for all groups and the SHOWSET G commands.
If a setting named VALID or LOGVAL is displayed, it will have a value of N. This
signifies that default settings have been loaded. Execute the SET G command to
enter the correct global settings for your application, and set VALID to Y. Note that
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