Demand calculation methods

Power demand is the energy accumulated during a specified period divided by the length of the period. Current demand is calculated using arithmetical integration of the current rms values during a time period, divided by the length of the period. How the meter performs this calculation depends on the selected method. To be compatible with electric utility billing practices, the meter provides the block interval power/current demand calculations. The default demand calculation is set to a fixed block with a 15-minute interval.

In the block interval demand method, select a block of time that the meter uses for the demand calculation. You can choose how the meter handles the block of time (interval). 3 different modes are possible:

• Fixed block - Select an interval from the range 10, 15, 20, 30, 60 minutes. The meter calculates and updates the demand at the end of each fixed interval.

• Sliding block - Select an interval from the range 10, 15, 20, 30, 60 minutes. For demand intervals less than 15 minutes, the value is updated every 15 seconds. For demand intervals of 15 minutes and greater, the demand value is updated every 60 seconds. The meter displays the demand value for the last completed interval.

• Rolling block - Select an interval and a subinterval. Demand is updated at the end of each subinterval. The meter displays the demand value for the last completed interval.

  NOTE: The subinterval must divide evenly into the interval (for example, three 5-minute (5 x 60 seconds) subintervals for a 15-minute interval).

The following figures illustrate the 3 ways to calculate demand power using the block method. For illustration purposes, the interval is set to 15 minutes.