MicroLogic Active E/EP/Ei Demand Value Calculation

Presentation

The MicroLogic Active E/EP/Ei control unit calculates the demand values of phase and average currents.

Each maximum demand value (peak) is stored in memory.

Definition

The demand value is the average value of a quantity over a specified period of time (interval).

Current Demand Value Calculation

The current demand is calculated using the thermal method. The thermal current demand calculates the demand based on a thermal response which mimics the analog thermal demand meters, as shown in the following illustration:

The time constant of integration (current demand calculation interval) is fixed and set at 15 minutes.

Power Demand Value Calculation

The power demand value is calculated using arithmetical integration of power RMS values over a period of time, divided by the length of the period. The result is equivalent to the energy accumulated during the period of time divided by the length of the period. In the MicroLogic Active control unit the power demand is calculated according to the sliding block method.

At the end of the power demand calculation interval, and then every one tenth of the interval, that is every 1 minute 30 seconds:

• The demand value over the interval is calculated and updated.

• Calculation of a new demand value is initialized on a new interval:

  • By eliminating the contribution of the first tenth of the previous interval

  • By adding the contribution of the latest tenth