Mikro DPM680, Instruction Manual, Page: 81 / 84

81
appEnDix B
nuMEriCal METHoDs
b.1 DeManD calculation
Demand parameters are used to show average values over a demand interval.
This power meter calculates the demand quantity by using the sliding block method. In this method,
the demand interval is divided into n sub intervals. For each sub interval s, the quantity average, qs is
taken. Finally, the demand quantity is the average of the n consecutive sub interval quantity averages
over the demand interval, i.e. Σ(qs)/n . The demand quantity is therefore updated at the expiry of each
sub interval.
In the example shown in the figure below for 3 sub intervals per demand interval, sub interval average
currents, is1 to is5 are taken over sub intervals 1 to 5. At the end of sub interval 3, the demand current
id1 is calculated from the average of the last 3 sub interval average currents, i.e. id1 = (is1 + is2 + is3)
/ 3. This process will repeat again at the end of sub interval 4 where id2 = (is2 + is3 + is4) / 3.
Appendix
B.1