GE Multilin F60 Feeder Protection System 5-415 SETTINGS 5.2 PRODUCT SETUP55.2.10 DEMANDPATH: SETTINGS Ö PRODUCT SETUP ÖØ DEMANDThe relay measures current demand on each phase, and three-phase demand for real, reactive, and apparent power. Cur-rent and Power methods can be chosen separately for the convenience of the user. Settings are provided to allow the userto emulate some common electrical utility demand measuring techniques, for statistical or control purposes. If the CRNTDEMAND METHOD is set to "Block Interval" and the DEMAND TRIGGER is set to “Off”, Method 2 is used (see below). IfDEMAND TRIGGER is assigned to any other FlexLogic™ operand, Method 2a is used (see below).The relay can be set to calculate demand by any of three methods as described below:CALCULATION METHOD 1: THERMAL EXPONENTIALThis method emulates the action of an analog peak recording thermal demand meter. The relay measures the quantity(RMS current, real power, reactive power, or apparent power) on each phase every second, and assumes the circuit quan-tity remains at this value until updated by the next measurement. It calculates the 'thermal demand equivalent' based on thefollowing equation:(EQ 5.6)where: d = demand value after applying input quantity for time t (in minutes)D = input quantity (constant), and k = 2.3 / thermal 90% response time.The 90% thermal response time characteristic of 15 minutes is illustrated below. A setpoint establishes the time to reach90% of a steady-state value, just as the response time of an analog instrument. A steady state value applied for twice theresponse time will indicate 99% of the value.Figure 5–3: THERMAL DEMAND CHARACTERISTICCALCULATION METHOD 2: BLOCK INTERVALThis method calculates a linear average of the quantity (RMS current, real power, reactive power, or apparent power) overthe programmed demand time interval, starting daily at 00:00:00 (i.e. 12:00 am). The 1440 minutes per day is divided intothe number of blocks as set by the programmed time interval. Each new value of demand becomes available at the end ofeach time interval.CALCULATION METHOD 2a: BLOCK INTERVAL (with Start Demand Interval Logic Trigger)This method calculates a linear average of the quantity (RMS current, real power, reactive power, or apparent power) overthe interval between successive Start Demand Interval logic input pulses. Each new value of demand becomes available atthe end of each pulse. Assign a FlexLogic™ operand to the DEMAND TRIGGER setting to program the input for the newdemand interval pulses. DEMANDCRNT DEMAND METHOD:Thermal ExponentialRange: Thermal Exponential, Block Interval,Rolling DemandMESSAGE POWER DEMAND METHOD:Thermal ExponentialRange: Thermal Exponential, Block Interval,Rolling DemandMESSAGE DEMAND INTERVAL:15 MINRange: 5, 10, 15, 20, 30, 60 minutesMESSAGE DEMAND TRIGGER:OffRange: FlexLogic™ operandNote: for calculation using Method 2ad t( ) D 1 e kt––( )=842787A1.CDRTime (minutes)Demand (%)
