GE Power Quality Meter Series Instruction Manual page 66

4.2 S1 PQM SETUP
• DEMAND: The PQM calculates demand using the three methods described in the table below.
METHOD
Thermal
Exponential
4
Block Interval This selection calculates a linear average of the quantity (RMS current, real power,
Rolling
Demand
• CURRENT DEMAND TYPE: Three current demand calculation methods are available: thermal exponen-
tial, block interval, and rolling demand (see the table above). The current demand for each phase and neu-
tral is calculated individually.
• CURRENT DEMAND TIME INTERVAL: Enter the time period over which the current demand calculation
is to be performed.
• POWER DEMAND TYPE: Three phase real/reactive/apparent power demand calculation methods are
available: thermal exponential, block interval, and rolling demand (see the table above). The three phase
real/reactive/apparent power demand is calculated.
• POWER DEMAND TIME INTERVAL: Enter the time period over which the power demand calculation is to
be performed.
• ENERGY COST PER kWh: Enter the cost per kWh that is charged by the local utility.
• TARIFF PERIOD START TIME: Enter the start time for each of the three tariff period calculations.
• TARIFF PERIOD COST PER MWH: Enter the cost per MWh for each of the three tariff periods.
4-10
DESCRIPTION
This selection emulates the action of an analog peak-recording thermal demand meter.
The PQM measures the average quantity (RMS current, real power, reactive power, or
apparent power) on each phase every minute and assumes the circuit quantity remains
at this value until updated by the next measurement. It calculates the "thermal demand
equivalent" based on the following equation:
kt
–
d t ( ) ( ) d
D 1 e = demand value after applying input quantity for time t (in min.)
= –
D = input quantity (constant)
k = 2.3 / thermal 90% response time
100
80
60
40
20
0
0
The above graph shows the thermal response characteristic for a thermal 90% response
time of 15 minutes. 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).
reactive power, or apparent power) over the programmed demand TIME INTERVAL. Each
new value of demand becomes available at the end of each time interval.
This selection calculates a linear average of the quantity (RMS current, real power,
reactive power, or apparent power) over the programmed demand TIME INTERVAL (in the
same way as Block Interval). The value is updated every minute and indicates the
demand over the time interval just preceding the time of update.
PQM Power Quality Meter
3 6 9 12 15 18
Time (min)
4 PROGRAMMING
21 24 27 30
GE Power Management