Electrical demand reduction examples

This example shows a partial wiresheet view of an ElectricDemandLimit component configured for shedding energy loads. The current time period in this example is Demand Period2.

Figure 1. Wiresheet view of an EDL example application

Power Input (1) reflects total demand, which is linked into the EDL component Power Input property. This is a single input value, therefore the power sources need to be totaled before linking because there is more than one meter supplying actual electrical demand data. This demand level value is expected to change in response to load shedding.

Demand Interval (2) is set to update every 15 minutes.

Percent Interval Elapsed (3) is set to 25 percent, which adds more weight to current demand and less weight to historical demand for each calculation of the Projected Demand Average.

Demand Limit Periods 1 and 2 (4) are set to 1000 and 2000, respectively. These values specify the demand levels that initiate power shedding.

Demand Period (5) start times for periods 1 and 2 are set to 0000 (midnight) and 0800 (8 am) respectively. Demand Period3 Start time is not shown. These times specify the start time for each of the demand periods.

Power Shed Levels1–3 settings (6) are based on these estimates:

By shedding loads associated with Power Shed Level 1, the amount of demand will decrease by 900 kW.
Power Shed Levels 2 and 3 should be set at 910 and 920 respectively.

If these estimates are correct, shedding at level 3 reduces demand by the sum of all three shed levels: (900+910+920)=270330 kW.

Projected Demand Average (7) has a current value of 2051.

Since this value is greater than the demand limits, the component initiates shedding and displays this message (8): “SHEDDING REQUIRED ! Projected demand is 2051”.

The Shed Out (9) value of 1.0 indicates that one level is to be shed. This property links to a Shed Control component, which configures the specific Shed Level (1–16) links into Boolean controls. In the example, these controls shut off power to Plant_A, Plant_B, and Plant_C, with Shed Level(1, 2, and 3), respectively. In addition, the ShedControl component’s out1 value (10) links to a SetpointLoadShed component that uses a setpoint offset to reduce power usage.

You can also link from the Shed Out property to other energy components, such as a Setpoint Offset component (also shown here).

With a Shed Level1 in effect, Power Input is at 2100, and the Projected Average Demand value is 2051, still greater than the Demand Limit Period2 value of 2000. The Power Shed Level2 value (estimate) indicates that invoking a Power Shed Level2 yields a decrease of 910kW and brings the demand down below the limit. If this estimate is fairly accurate, actual power usage should drop and the Power Input value should lower to below the Demand Limit Period2 value.

The following wire sheet provides a close-up example of how to configure the ShedControl component.

The Primary Shed Level (1) links from an EDL component. Its value is 1.0. No Secondary Shed Level is used.

Out1, 2, and 3 (2) link to Boolean controls that are set to turn off power to Plant_A, B, and C, respectively.

The current Primary Shed Level of 1.0 sets out1 (3) to false and the Plant_A Boolean control status (4) to false. This should turn off power to any power consuming devices that are linked to this object.

The out1 value is also linked to the SetpointLoadShed component (5), which adjusts a setpoint to reduce the electrical demand.

If more shed levels are needed, the component sets out2 and out3 to false. If shed levels are no longer needed, the component invokes a restoration, which restores out3, out2, and out1, in that order, to null as allowed by the current shed level.