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CHAPTER 4: SETPOINTS
MONITORING
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
4–279
k-FACTOR
Range: 1.00 to 1.50 in steps of 0.01
Default: 1.10
This setting defines the current level at which the power system element is considered
to be overloaded. If the current exceeds the k x I
b
threshold, the thermal overload
protection reacts by accumulating thermal capacity.
OVERLOAD CURVE
Range: IEC, FlexCurve A, FlexCurve B, FlexCurve C, FlexCurve D
Default: IEC
The thermal overload curve determines the thermal limit overload conditions that can
damage the power system element. The overload curve can take one of five formats:
IEC, FlexCurve A, FlexCurve B, FlexCurve C, or FlexCurve.
OPERATE TIME CONSTANT
Range: 0.0 to 1000.0 min in steps of 0.1 min
Default: 45 min
This setting specifies thermal operate time constant for IEC curves as defined by the IEC
255-8 standard equations (EQN 1 & 2). When the IEC curves are selected, the thermal
overload element calculates the time to operate (top) using the IEC255-8 cold curve and
IEC255-8 hot curve equations, and increases thermal capacity as defined by the
equation EQN 5.
TD MULTIPLIER
Range: 0.00 to 600.00 in steps of 0.01 when the thermal model curve is a FlexCurve
Default: 1.00
This setting is only applicable when the Overload Curve setting is programmed as one of
the FlexCurves (A, B, C, or D). TD Multiplier is used to shift the overload curve on the time
axis to create a family of the different curves. The TD Multiplier value is used to select the
curve that best matches the thermal characteristics of the protected power system
element.
This setting allows the selection of a multiple of the base curve shape (where the time
dial multiplier = 1) with the curve shape setting. For example, all times for a TDM = 10 are
ten times the multiplier 1, or base curve values.
RESET TIME CONSTANT
Range: 0.0 to 1000.0 min in steps of 0.1 min
Default: 45 min
This setting specifies the thermal reset rime constant for IEC curves, to determine the
reset time using EQN 4 to reset the thermal overload protection.
MIN RESET TIME
Range: 0.0 to 1000.0 min in steps of 0.1 min
Default: 10.0 min
This setting specifies the minimum time to reset the thermal overload protection. This
setting is only applicable to IEC curves.
THERMAL RESET
Range: Off, Any FlexLogic operand
Default: Off
In case of emergency, the thermal memory and thermal OP output operand can be
reset using the Thermal Reset operand.