User Guide SL7000 IEC7
42
6.9.4.1.
Demand channels
For demand registering purposes the meter can be configured with up to ten independent demand channels,
each channel being selected from the list of available measured energy quantities.
In addition, the calculated aggregate power factor can be allocated to a demand channel.
Tariffs are applied to these demand channels, with the exception of the aggregate power factor channel.
At any time, several tariff rates can be active for a particular demand channel and it is possible to have different
tariff rate configurations in each demand channel.
6.9.4.2.
Demand registers
The meter records energy demand in up to twenty-four individual demand registers. Each of the meter demand
channels can have a maximum allocation of eight demand registers from within this limit. The demand registers
are dedicated to recording the average energy demand over a fixed time known as the
integration period
.
6.9.4.3.
Integration period
Calculating demand over a period of time helps avoid any short peak values (typically, transients caused by
starting heavy inductive loads) from affecting the calculation.
The integration period has:
•
a programmable duration - in discrete (sub multiples of 60) steps from 1 minute to 60 minutes
•
two modes of operation:
•
Fixed
(or block mode)
•
Sliding
The meter applies the selected integration period mode and duration value across all demand channels.
During the integration period a set of
rising values
are available that represent the currently calculated demand
for each demand channel. These rising values are updated every second by integrating the energy consumed
since the beginning of the period over the total duration of the period.
At the end of each completed integration period (EOI):
•
the demand calculations are made
•
if the current demand value is greater than the previous maximum demand value recorded, the new value is
time stamped and replaces the previous maximum
•
the current demand registers are set to zero
•
the EOI time-stamping is carried out and a new integration period is started
Fixed or block mode
In the fixed or block mode the integration periods have a single predefined duration value.
The illustration below shows two successive fixed or block integration periods with, for example, a duration of 15
minutes. The rising demand value is based on a constant load:
1
Rising value
2
Integration period duration
3
Actual demand value
4
Elapsed time
