ABB REL 356

ABB REL 356 Current Differential Protection
2-8
Installation, Operation and Maintenance
REL 356 FRONT PANEL DISPLAY
The front panel display consists of a vacuum fluorescent display set of seven LED indicators, seven key switches.
Vacuum Fluorescent Display
The vacuum fluorescent or LCD display contains 2X4 alphanumeric characters for the function field and the value field.
The display is blocked momentarily every minute for the purpose of self-check; this will not affect the relay protection
function. A “DISPLAY SAVER” feature turns-off the display if no key activity for 3 minutes is detected.
Indicators
There are 7 LED indicators on the front panel display:
• 1 “relay-in-service” indicator
• 1 “value accepted” indicator
• 5 display-select indicators
When the “Relay-in-Service” LED illuminates, the REL 356 Relay is in service, there is dc power to the relay and the
relay has passed the self-check and self-test. The LED is turned “OFF” if the Relay-in-service relay has at least one of
the internal failures shown in the “Test” mode.
The “Value Accepted” LED flashes only once, to indicate that a value has been entered successfully.
The 5 indicators used for the display selection are:
• Settings
• Volts/Amps/Angle
• LAST FAULT
• PREVIOUS FAULT
• Test
One of these indicators is always illuminated, indicating the mode selected.
Key Switches
The front panel contains 7 keys:
• Display Select
• Reset Targets
• Function Raise
• Function Lower
• Value Raise
• Value Lower
• Enter (recessed for security purposes)
The “Display Select” key is used to select one of the five display modes, which is indicated when the proper LED
illuminates. When a fault is detected, the “LAST FAULT” flashes once per second. If two faults are recorded, the “LAST
FAULT” flashes twice per second, and the prior fault will be moved from “LAST FAULT” to “PREVIOUS FAULT”. The
new fault data will be stored in the “LAST FAULT” register. By depressing the “Reset Targets” key, the flashing LED
indicators are cleared, and the LED will revert back to the Metering mode. The information in the “PREVIOUS FAULT”