This ED algorithm generally applies to only thermal generation units that have cost characteristics of the type discussed here. The hydro units have to be dispatched with different considerations. Although there is no cost for the water, the amount of water available is limited over a period, and the displacement of fossil fuel previously computed hydro optimization, the water worth can be used to dispatch the hydro unit from a by this water determines its worth. Thus, if the water usage limitation over a period is known, LFC and the ED functions both operate automatically in real time but with vastly different time period Both adjust generation levels, but LFC does it every few seconds to follow the load variation, while ed does it every few minutes to assure minimal cost. Conflicting control action is avoided by coordinating the control errors. If the unit control errors from lfc and ed are in the same direction there is no conflict otherwise a logic is set to either follow load (permissive control) or follow ec (mandatory control). Reserve monitoring Maintaining enough reserve capacity is required in case generation is lost. Explicit formulas are followed to determine the spinning(already synchronized)and ready(10 min)reserves required. The availability can be assured by the operator manually, or, as mentioned previously, the ED can also reduce the upper dispatchable limits of the generators to keep such generation available Interchange Transaction Scheduling The contractual exchange of power between utilities has to be taken into account by the LFC and ED functions. This is done by calculating the net interchange(sum of all the buy and sale agreements)and adding this to the generation needed in both the LFC and ED. Since most interchanges begin and end on the hour, the net interchange is ramped from one level to the new over a 10-or 20-min period straddling the hour. The programs achieve this automatically from the list of scheduled transactions 4 Load management SCADA, with its relatively expensive RTUs installed at distribution substations, can provide status and mea- surements for distribution feeders at the substation. Distribution automation equipment is now available to measure and control at locations dispersed along distribution circuits. This equipment can monitor sectional izing devices(switches, interruptors, fuses), operate switches for circuit reconfiguration, control voltage, read customers'meters, implement time-dependent pricing(on-peak, off-peak rates), and switch customer equip- ment to manage load. This equipment requires significantly increased functionality at distribution control centers Distribution control center functionality varies widely from company to company, and the following list is evolving rapidly. Data acquisition: Acquires data and gives the operator control over specific devices in the field Includes data processing, quality checking, and storage Feeder switch control: Provides remote control of feeder switches Tagging and alarms: Provides features similar to SCADA. Diagrams and maps: Retrieves and displays distribution maps and drawings. Supports device selection from these displays Overlays telemetered and operator-entered data on displays Preparation of switching orders: Provides templates and information to facilitate preparation of instruc ions necessary to disconnect, isolate, reconnect, and reenergize equipment. Switching instructions: Guides operator through execution of previously prepared switching orders. Trouble analysis: Correlates data sources to assess scope of trouble reports and possible dispatch of wor Fault location: Analyzes available information to determine scope and location of fault Service restoration: Determines the combination of remote control actions which will maximize resto- ration of service Assists operator to dispatch work crews c 2000 by CRC Press LLC© 2000 by CRC Press LLC This ED algorithm generally applies to only thermal generation units that have cost characteristics of the type discussed here. The hydro units have to be dispatched with different considerations. Although there is no cost for the water, the amount of water available is limited over a period, and the displacement of fossil fuel by this water determines its worth. Thus, if the water usage limitation over a period is known, say from a previously computed hydro optimization, the water worth can be used to dispatch the hydro units. LFC and the ED functions both operate automatically in real time but with vastly different time periods. Both adjust generation levels, but LFC does it every few seconds to follow the load variation, while ED does it every few minutes to assure minimal cost. Conflicting control action is avoided by coordinating the control errors. If the unit control errors from LFC and ED are in the same direction, there is no conflict. Otherwise, a logic is set to either follow load (permissive control) or follow economics (mandatory control). Reserve Monitoring Maintaining enough reserve capacity is required in case generation is lost. Explicit formulas are followed to determine the spinning (already synchronized) and ready (10 min) reserves required. The availability can be assured by the operator manually, or, as mentioned previously, the ED can also reduce the upper dispatchable limits of the generators to keep such generation available. Interchange Transaction Scheduling The contractual exchange of power between utilities has to be taken into account by the LFC and ED functions. This is done by calculating the net interchange (sum of all the buy and sale agreements) and adding this to the generation needed in both the LFC and ED. Since most interchanges begin and end on the hour, the net interchange is ramped from one level to the new over a 10- or 20-min period straddling the hour. The programs achieve this automatically from the list of scheduled transactions. 67.4 Load Management SCADA, with its relatively expensive RTUs installed at distribution substations, can provide status and mea￾surements for distribution feeders at the substation. Distribution automation equipment is now available to measure and control at locations dispersed along distribution circuits. This equipment can monitor sectional￾izing devices (switches, interruptors, fuses), operate switches for circuit reconfiguration, control voltage, read customers’ meters, implement time-dependent pricing (on-peak, off-peak rates), and switch customer equip￾ment to manage load. This equipment requires significantly increased functionality at distribution control centers. Distribution control center functionality varies widely from company to company, and the following list is evolving rapidly. • Data acquisition: Acquires data and gives the operator control over specific devices in the field. Includes data processing, quality checking, and storage. • Feeder switch control: Provides remote control of feeder switches. • Tagging and alarms: Provides features similar to SCADA. • Diagrams and maps: Retrieves and displays distribution maps and drawings. Supports device selection from these displays. Overlays telemetered and operator-entered data on displays. • Preparation of switching orders: Provides templates and information to facilitate preparation of instruc￾tions necessary to disconnect, isolate, reconnect, and reenergize equipment. • Switching instructions: Guides operator through execution of previously prepared switching orders. • Trouble analysis: Correlates data sources to assess scope of trouble reports and possible dispatch of work crews. • Fault location: Analyzes available information to determine scope and location of fault. • Service restoration: Determines the combination of remote control actions which will maximize resto￾ration of service. Assists operator to dispatch work crews