User's Manual

ANSI Electric Meter v3.1 User’s Guide 71
Demand Calculations and Settings
The ANSI v3.1 meter (83011-83301) offers various types of demand calculations that
can be performed to measure the peak active and reactive power being delivered to
the system over a designated time period. Demand measurements are useful in that
they provide information on peak usage as opposed to accumulation over time, and by
using averages instead of instantaneous maximum power values are not impacted by
spikes and short surges. This chapter describes the different demand calculations
you can make with the meter.
Demand metering is an optional feature for the ANSI version 3.1 meter (83011-
83301). Please contact your Echelon sales representative for more information on
this. Although demand metering can be enabled and configured in the field, Echelon
strongly recommends anticipating its use and configuring the demand settings before
installing your meters, so that system-wide resource allocations are not impacted
later.
Demand Settings
In general, demand values (D) are calculated by measuring the energy (E) levels at
the start (t-1) and end (t) of a time period, and dividing the difference between those
two power levels by the time that has elapsed between them (
) to come up with
an average power value for that interval.
You can customize exactly how the demand calculations will be made by configuring
the demand settings for a meter, including the sub-interval and the main interval.
You can create one of two demand scenarios, depending on how you configure these
settings:
Rolling demand. Rolling demand uses the interval and sub-interval to create
interlaced measurement periods. This provides a way to calculate the peak
power usage for a set period of time, and the meter continues to update the
value as more time elapses to generate a rolling average. In this scenario,
the sub-interval determines how frequently the value will be updated. The
main interval determines the length of time for which demand measurements
will be made. Each time a sub-interval elapses, the data for the oldest sub-
interval is thrown out and replaced by the data for the most recent sub-
interval, and the demand is measured again.
Note: To establish the main interval value, you need to set the value of the demand
multiplier. The demand multiplier determines how many sub-intervals exist
per main interval, and so the duration of the main interval is determined by
multiplying the sub-interval by the demand multiplier. You can set the sub-
interval to any value between 1 and 60 minutes. You can set the demand
multiplier to any value between 1 and 15.
For example, if you wanted to measure the peak power usage for a meter for
45-minute periods, and you wanted an updated value to be reported every
five minutes, you could use rolling demand. You would set the sub-interval