GE F60 UR Series, Instruction Manual

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GE Multilin F60 Feeder Protection System 5-41
5 SETTINGS 5.2 PRODUCT SETUP
5
5.2.10 DEMAND
PATH: SETTINGS
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PRODUCT SETUP
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DEMAND
The 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 user
to emulate some common electrical utility demand measuring techniques, for statistical or control purposes. If the
CRNT
DEMAND METHOD
is set to "Block Interval" and the
DEMAND TRIGGER
is set to “Off”, Method 2 is used (see below). If
DEMAND 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 EXPONENTIAL
This 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 the
following 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 reach
90% of a steady-state value, just as the response time of an analog instrument. A steady state value applied for twice the
response time will indicate 99% of the value.
Figure 5–3: THERMAL DEMAND CHARACTERISTIC
CALCULATION METHOD 2: BLOCK INTERVAL
This method calculates a linear average of the quantity (RMS current, real power, reactive power, or apparent power) over
the programmed demand time interval, starting daily at 00:00:00 (i.e. 12:00 am). The 1440 minutes per day is divided into
the number of blocks as set by the programmed time interval. Each new value of demand becomes available at the end of
each 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) over
the interval between successive Start Demand Interval logic input pulses. Each new value of demand becomes available at
the end of each pulse. Assign a FlexLogic™ operand to the
DEMAND TRIGGER
setting to program the input for the new
demand interval pulses.
„
DEMAND
„
CRNT DEMAND METHOD:
Thermal Exponential
Range: Thermal Exponential, Block Interval,
Rolling Demand
MESSAGE
POWER DEMAND METHOD:
Thermal Exponential
Range: Thermal Exponential, Block Interval,
Rolling Demand
MESSAGE
DEMAND INTERVAL:
15 MIN
Range: 5, 10, 15, 20, 30, 60 minutes
MESSAGE
DEMAND TRIGGER:
Off
Range: FlexLogic™ operand
Note: for calculation using Method 2a
d t
( )
D 1 e
kt –
–
( )
=
842787A1.CDR
Time (minutes)
Demand
(%)