CHAPTER 4: SETPOINTS MONITORING889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–279k-FACTORRange: 1.00 to 1.50 in steps of 0.01Default: 1.10This setting defines the current level at which the power system element is consideredto be overloaded. If the current exceeds the k x Ib threshold, the thermal overloadprotection reacts by accumulating thermal capacity.OVERLOAD CURVERange: IEC, FlexCurve A, FlexCurve B, FlexCurve C, FlexCurve DDefault: IECThe thermal overload curve determines the thermal limit overload conditions that candamage the power system element. The overload curve can take one of five formats:IEC, FlexCurve A, FlexCurve B, FlexCurve C, or FlexCurve.OPERATE TIME CONSTANTRange: 0.0 to 1000.0 min in steps of 0.1 minDefault: 45 minThis setting specifies thermal operate time constant for IEC curves as defined by the IEC255-8 standard equations (EQN 1 & 2). When the IEC curves are selected, the thermaloverload element calculates the time to operate (top) using the IEC255-8 cold curve andIEC255-8 hot curve equations, and increases thermal capacity as defined by theequation EQN 5.TD MULTIPLIERRange: 0.00 to 600.00 in steps of 0.01 when the thermal model curve is a FlexCurveDefault: 1.00This setting is only applicable when the Overload Curve setting is programmed as one ofthe FlexCurves (A, B, C, or D). TD Multiplier is used to shift the overload curve on the timeaxis to create a family of the different curves. The TD Multiplier value is used to select thecurve that best matches the thermal characteristics of the protected power systemelement.This setting allows the selection of a multiple of the base curve shape (where the timedial multiplier = 1) with the curve shape setting. For example, all times for a TDM = 10 areten times the multiplier 1, or base curve values.RESET TIME CONSTANTRange: 0.0 to 1000.0 min in steps of 0.1 minDefault: 45 minThis setting specifies the thermal reset rime constant for IEC curves, to determine thereset time using EQN 4 to reset the thermal overload protection.MIN RESET TIMERange: 0.0 to 1000.0 min in steps of 0.1 minDefault: 10.0 minThis setting specifies the minimum time to reset the thermal overload protection. Thissetting is only applicable to IEC curves.THERMAL RESETRange: Off, Any FlexLogic operandDefault: OffIn case of emergency, the thermal memory and thermal OP output operand can bereset using the Thermal Reset operand.
