GE Multilin 850

CHAPTER 4: SETPOINTS PROTECTION
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–183
The pickup is calculated as follows:
I
pickup
= K * I
base
I
pickup
is the pickup current (xCT) setting. K is a factor reflecting the relay current
measurement error. I
base
is the permissible current of the equipment to be thermally
protected (in many cases this is the maximum continuous current for the equipment
within its thermal limits)
ALARM
Range: 70.0 to 110.0% in steps of 0.1%
Default: 80.0%
The setting sets the Alarm level for the accumulated thermal capacity above which the
element generates an alarm. The Alarm signal can be displayed by the user-
programmable LED.
HEAT TIME CONSTANT (τ
H
)
Range: 3.0 to 600.0 min in steps of 0.1 min
Default: 6.0 min
The time constant is used to compute the thermal capacity when the squared load/
Pickup ratio at each time step is greater than the thermal capacity computed in the
previous time step.
COOL TIME CONSTANT (τ
C
)
Range: 1.00 to 6.00 x 
H
in steps of 0.01 x 
H
Default: 6.0 min
The time constant is used to compute the thermal capacity when the squared load/
Pickup ratio at each time step is less than the thermal capacity computed in the
previous time step.
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
The element is blocked when the operand is asserted.
OUTPUT RELAY X
For details see Common Setpoints
.
Each relay can be selected to become either energized or de-energized when operated,
and to operate as latched, self-resetting or pulsed.
EVENTS
Range: Enabled, Disabled
Default: Enabled
The selection of the Enabled setting enables the events of the function.
TARGETS
Range: Self-Reset, Latched, Disabled
Default: Self-Reset
The setting is used to define the operation of an element target message. When set to
“Disabled”, no target message is issued upon operation of the element. When set to
“Self-Reset”, the target message and LED indication follow the operate state of the
element, and self-resets once the operate element condition clears. When set to
“Latched”, the target message will remain visible after the element output returns to
logic 0 until a RESET command is received by the relay.