Rockwell Automation 1404-M4_M5_M6_M8 Powermonitor 3000 User Manual, Firmware rev. 3.0 or LATER - Manual (Page 37)

Publication 1404-UM001F-EN-P - November 2009 37
Powermonitor 3000 Unit Operations Chapter 3
Instantaneous
The power monitor computes instantaneous demand by substituting
the elapsed interval duration for the total interval duration (T) in the
demand equation. It is therefore identical to the standard computation
except it integrates the power only over the elapsed interval duration
and calculates the average value over the elapsed duration. The
modified equation thus becomes.
First Order Projection
The first order demand projection does the following:
•
Utilizes the instantaneous demand as a starting point
•
Computes the trend of the instantaneous demand
•
Computes the time remaining in the interval
•
Performs a first order projection of what the final demand is at
the end of the interval.
This method may be useful where your system has a significant base
load with additional loads that are switched in and out during the
interval.
Second Order Projection
The second order demand projection begins with the first order
projection, then it does the following:
•
Computes the rate of change of the first order trend
•
Computes the time remaining in the interval
•
Performs a second order projection of what the final demand is
at the end of the interval
This method may be useful where your power system has little or no
base load and a load profile that increases over the duration of the
interval. A second order projection is more sensitive to rapid load
changes than the other methods.
Demand
1
t2 t1 –
---------------- P t ( ) t d
t1
t2
∫ • =
(t2 - t1) = Elapsed interval duration and is less than T