CHAPTER 4: PROGRAMMING
S1 PQM SETUP
PQM POWER QUALITY METER – INSTRUCTION MANUAL
4–11
•
DEMAND:
The PQM calculates demand using the three methods described in the table
below.
•
CURRENT DEMAND TYPE:
Three current demand calculation methods are available:
thermal exponential, block interval, and rolling demand (see the table above). The
current demand for each phase and neutral 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 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 KWH:
Enter the cost per kWh for each of the three tariff
periods.
METHOD
DESCRIPTION
Thermal
Exponential
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:
= demand value after applying input quantity for time
t
(in min.)
D
= input quantity (constant)
k
= 2.3 / thermal 90% response time
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).
Block
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.
Each new value of demand becomes available at the end of each time interval.
Rolling
Demand
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.
d t
( )
D
1
e
kt
–
–
(
)
d
=
T
i
me (m
in
)
0
20
40
60
80
100
0
3
6
9
12
15
18
21
24
27
30
Dema
n
d(
%
)
Содержание Multilin PQM
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