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Responding to Coincident Demand Rates
Introduction Coincident demand rates are those where the customer is charged for demand usage at the time the utility supplying power experiences its peak. These rates provide revenue safeguards for the supplying utility as well as opportunities for the customer to save money. The Dencor 300C Energy Administration System has several control features that make it especially effective for use with coincident demand rates. Several of these features will be illustrated here. Three Demand Set Points Three demand set points may be used to respond to changes in demand charges at different times. By creative use of methods to switch from one demand set point to another an effective response to coincident demand rates can be structured. Example Using a Utility Load Management Receiver to Activate Critical Demand Set Points for Coincident Demand Control Dencor 300C Energy Administration Systems may be used by customers on coincident demand billing rates to respond to utility signals indicating the status of rates. One or more Utility Load Management Receiver contacts may be used to control one or more Digital Inputs on the 300C as shown in Figure 1. These inputs may be used by the utility to send notice of coincident demand peak periods or other control information. The contacts may be used to signal power supplier peak periods, distribution utility peaks or substation peaks. The customer may use the information to specify how to respond. The response will include a decision about which demand Set Point to make active. Four digital inputs are available for several different functions. Five of these functions are shown in Figure 2. Setting the demand to a critical set point is one of these functions. Using a Telephone to Activate Critical Demand Control A telephone connection, as shown in Figure 3, from the utility to the customer's 300C Energy Administration System provides many benefits. The utility can send brief commands indicating that a power supply peak or a distribution peak is occurring. If real-time pricing is used, pricing information may be transmitted. The utility can monitor the responses of each customer to coincident demand or price signals. The utility can also send start and stop times for critical set point control or direct relay control to the 300C. These times can be specified over the phone using the Utility Critical Control Settings window shown in Figure 4. If the critical times are known in advance, they may be pre-set up to a week in advance. This method can also be used as an emergency backup in case the utility load management system is not functioning. Setting Utility On-Peak Times The Utility On-Peak Time Functions window shown in Figure 5 is used to specify the on-peak periods for each of the four seasons. This provides the basic demand control structure for time-of-use demand rates. Any time a critical demand set point is active it will take precedence over on-peak or off-peak set points. This is true even if the critical set point has a higher demand value than an off-peak or on-peak value. If the critical setting has not been activated, the on-peak value will be used, if the on-peak set point is active. If neither the on-peak nor critical set point is active, the off- peak set point is used. Hierarchy The Critical Utility Control Settings window entries have the highest priority followed by the Digital Input Settings functions. The Utility On-Peak Time Functions have the lowest priority. Thus, if a Digital Input is used to force an Off-Peak demand setting it will have priority over the on-peak time functions defined in the Utility On-Peak Time Functions window. Lock Relays Off During Critical Periods Other control functions are available to help control demand during critical periods. For example, the Relay Operation Selection window shown in Figure 6 allows any relay to be locked off during Critical control periods by us of the Critical Interval Override Latch. Summary The flexibility of the many available control functions make the Dencor 300C Energy Administration System the wise choice for both utilities and their customers when coincident demand rates are being used. The communication from the utility and the customer response is automatic. The customer response is available for immediate or delayed analysis so the effectiveness of a rate in achieving the desired objective is easily measured.
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