GE Multilin L30 Line Current Differential System 5-2435 SETTINGS 5.7 CONTROL ELEMENTS5(EQ 5.27)When current is less than the dropout level, I n > 0.97 × k × I B, the element starts decreasing the thermal energy:(EQ 5.28)In the above equations,• ∆t is the power cycle duration• n is the power cycle index• top(In) is the trip time calculated at index n as per the IEC255-8 cold curve or hot curve equations• trst(In) is the reset time calculated at index n as per the reset time equation• In is the measured overload RMS current at index n• En is the accumulated energy at index n• En – 1 is the accumulated energy at index n – 1The thermal overload protection element removes the THERMAL PROT 1 OP output operand when E < 0.05. In case ofemergency, the thermal memory and THERMAL PROT 1 OP output operand can be reset using THERM PROT 1 RESET setting.All calculations are performed per phase. If the accumulated energy reaches value 1 in any phase, the thermal overloadprotection element operates and only resets when energy is less than 0.05 in all three phases.The logic for the thermal overload protection element is shown below.Figure 5–110: THERMAL OVERLOAD PROTECTION SCHEME LOGICTable 5–32: TYPICAL TIME CONSTANTSPROTECTED EQUIPMENT TIME CONSTANT MINIMUM RESET TIMECapacitor bank 10 minutes 30 minutesOverhead line 10 minutes 20 minutesAir-core reactor 40 minutes 30 minutesBusbar 60 minutes 20 minutesUnderground cable 20 to 60 minutes 60 minutesE n E n 1–tΔt op In( )---------------+=E n E n 1–tΔt rst In( )---------------–=SETTINGSEnabled = 1FunctionOff = 0Block ANDSETTINGIA RMSSourceIB RMSIC RMSSETTINGSIA > k × IbK FactorIB > k × IbIC > k × IcBase CurrentORANDSETTINGTrip Time ConstantRUNE > 0.1SETTINGSReset Time ConstantRUNE < 0.1Minimum Reset TimeReset E to 0SETTINGOff = 0ResetLatchSRReset-dominantFLEXLOGIC OPERANDTHERMAL PROT 1 OPFLEXLOGIC OPERANDTHERMAL PROT 1 PKP827013A1.CDR
