4 HUMAN INTERFACES
NEUTRAL/GROUND: This LED indicates that neutral or ground was involved.
The user-programmable LEDs consist of 48 amber LED indicators in four columns. The operation of these LEDs is user-
defined. Support for applying a customized label beside every LED is provided. Default labels are shipped in the label pack-
age of every B90, together with custom templates. The default labels can be replaced by user-printed labels.
User customization of LED operation is of maximum benefit in installations where languages other than English are used to
communicate with operators. Refer to the User-programmable LEDs section in chapter 5 for the settings used to program
the operation of the LEDs on these panels.
b) STANDARD FACEPLATE
The standard faceplate consists of three panels with LED indicators, keys, and a communications port. The RESET key is
used to reset any latched LED indicator or target message, once the condition has been cleared (these latched conditions
can also be reset via the
The USER keys are not used in this unit.
IN SERVICE: Indicates that control power is applied; all monitored inputs/outputs and internal systems are OK; the
relay has been programmed.
TROUBLE: Indicates that the relay has detected an internal problem.
TEST MODE: Indicates that the relay is in test mode.
TRIP: Indicates that the selected FlexLogic operand serving as a Trip switch has operated. This indicator always
latches; the reset command must be initiated to allow the latch to be reset.
ALARM: Indicates that the selected FlexLogic operand serving as an Alarm switch has operated. This indicator is
PICKUP: Indicates that an element is picked up. This indicator is never latched.
EVENT CAUSE INDICATORS:
Events cause LEDs are turned on or off by protection elements that have their respective target setting selected as either
"Enabled" or "Latched". If a protection element target setting is "Enabled", then the corresponding event cause LEDs
remain on as long as operate operand associated with the element remains asserted. If a protection element target setting
is "Latched", then the corresponding event cause LEDs turn on when the operate operand associated with the element is
asserted and remain on until the RESET button on the front panel is pressed after the operand is reset.
All elements that are able to discriminate faulted phases can independently turn off or on the phase A, B or C LEDs. This
includes phase instantaneous overcurrent, phase undervoltage, etc. This means that the phase A, B, and C operate oper-
ands for individual protection elements are ORed to turn on or off the phase A, B or C LEDs.
VOLTAGE: Indicates voltage was involved.
CURRENT: Indicates current was involved.
FREQUENCY: Indicates frequency was involved.
OTHER: Indicates a composite function was involved.
PHASE A: Indicates phase A was involved.
Figure 4–18: LED PANEL 1
B90 Low Impedance Bus Differential System
4.3 FACEPLATE INTERFACE
menu). The RS232 port is for connection to a com-