Circuit continuity analysis: Analyzes circuit topology and device status to show electrically connected circuit segments( either energ ed or deenergized Power factor and voltage control: Combines substation and feeder data with predetermined operating parameters to control distribution circuit power factor and voltage levels Electrical circuit analysis: Performs circuit analysis, single-phase or three-phase, balanced or unbalanced. Load management: Controls customer loads directly through appliance switching(e.g, water heaters and indirectly through voltage cor Meter reading: Reads customers' meters for billing, peak demand studies, time of use tariffs. Provides remote connect/disconnect 67.5 Energy Management Generation control and ED minimize the current cost of energy production and transmission within the range f available controls. Energy management is a supervisory layer responsible for economically scheduling pro duction and transmission on a global basis and over time intervals consistent with cost optimization. For example, water stored in reservoirs of hydro plants is a resource that may be more valuable in the future and should, therefore, not be used now even though the cost of hydro energy is currently lower than thermal generation. The global consideration arises from the ability to buy and sell energy through the interconnected power system; it may be more economical to buy than to produce from plants under direct control. energy accounting processes transaction information and energy measurements recorded during actual operation basis of payment for energy sales and purchases Energy management includes the following functions: System load forecast: Forecasts system energy demand each hour for a specified forecast period of 1 to 7 days. Unit commitment: Determines start-up and shut-down times for most economical operation of thermal generating units for each hour of a specified period of 1 to 7 days Fuel scheduling: Determines the most economical choice of fuel consistent with plant requirements, fuel purchase contracts, and stockpiled fuel Hydro-thermal scheduling: Determines the optimum schedule of thermal and hydro energy production for each hour of a study period up to 7 days while ensuring that hydro and thermal constraints are not violated. Transaction evaluation: Determines the optimal incremental and production costs for exchange(pur- chase and sale) of additional blocks of energy with neighboring companies Transmission loss minimization: Recommends controller actions to be taken in order to minimize overall ecurity constrained dispatch: Determines optimal outputs of generating units to minimize production cost while ensuring that a network security constraint is not violated Production cost calculation: Calculates actual and economical production costs for each generating unit on an hourly basis 67.6 Security Control Power systems are designed to survive all probable contingencies. A contingency is defined as an event that causes one or more important components such as transmission lines, generators, and transformers to be unexpectedly removed from service. Survival means the system stabilizes and continues to operate at acceptable voltage and frequency levels without loss of load Operations must deal with a vast number of possible conditions experienced by the system, many of which are not anticipated in planning. Instead of dealing with the impossible task of analyzing all possible system states, security control starts with a specific state: the current state if executing the real-time network sequence; a postulated state if executing a study sequence. Sequence means sequential execution of programs that perform the following steps c 2000 by CRC Press LLC© 2000 by CRC Press LLC • Circuit continuity analysis: Analyzes circuit topology and device status to show electrically connected circuit segments (either energized or deenergized). • Power factor and voltage control: Combines substation and feeder data with predetermined operating parameters to control distribution circuit power factor and voltage levels. • Electrical circuit analysis: Performs circuit analysis, single-phase or three-phase, balanced or unbalanced. • Load management: Controls customer loads directly through appliance switching (e.g., water heaters) and indirectly through voltage control. • Meter reading: Reads customers’ meters for billing, peak demand studies, time of use tariffs. Provides remote connect/disconnect. 67.5 Energy Management Generation control and ED minimize the current cost of energy production and transmission within the range of available controls. Energy management is a supervisory layer responsible for economically scheduling pro￾duction and transmission on a global basis and over time intervals consistent with cost optimization. For example, water stored in reservoirs of hydro plants is a resource that may be more valuable in the future and should, therefore, not be used now even though the cost of hydro energy is currently lower than thermal generation. The global consideration arises from the ability to buy and sell energy through the interconnected power system; it may be more economical to buy than to produce from plants under direct control. Energy accounting processes transaction information and energy measurements recorded during actual operation as the basis of payment for energy sales and purchases. Energy management includes the following functions: • System load forecast: Forecasts system energy demand each hour for a specified forecast period of 1 to 7 days. • Unit commitment: Determines start-up and shut-down times for most economical operation of thermal generating units for each hour of a specified period of 1 to 7 days. • Fuel scheduling: Determines the most economical choice of fuel consistent with plant requirements, fuel purchase contracts, and stockpiled fuel. • Hydro-thermal scheduling: Determines the optimum schedule of thermal and hydro energy production for each hour of a study period up to 7 days while ensuring that hydro and thermal constraints are not violated. • Transaction evaluation: Determines the optimal incremental and production costs for exchange (pur￾chase and sale) of additional blocks of energy with neighboring companies. • Transmission loss minimization: Recommends controller actions to be taken in order to minimize overall power system network losses. • Security constrained dispatch: Determines optimal outputs of generating units to minimize production cost while ensuring that a network security constraint is not violated. • Production cost calculation: Calculates actual and economical production costs for each generating unit on an hourly basis. 67.6 Security Control Power systems are designed to survive all probable contingencies. A contingency is defined as an event that causes one or more important components such as transmission lines, generators, and transformers to be unexpectedly removed from service. Survival means the system stabilizes and continues to operate at acceptable voltage and frequency levels without loss of load. Operations must deal with a vast number of possible conditions experienced by the system, many of which are not anticipated in planning. Instead of dealing with the impossible task of analyzing all possible system states, security control starts with a specific state: the current state if executing the real-time network sequence; a postulated state if executing a study sequence. Sequence means sequential execution of programs that perform the following steps: