The electric industry operates on a just-in-time basis. This is because unlike solid, liquid, or gaseous forms of energy, there is as of yet no practical and economic way to store electrical energy in the amounts that modern society uses on a second-by-second basis. Consequently, the supply of electric energy must be produced so as to always meet demand. Furthermore, the flow of electric energy cannot be controlled in the same way that solid, liquid, and gaseous flows of energy can be. Electric energy can be put onto the grid and taken off the grid. But the energy generated at a particular power plant cannot be sent to a particular load. Instead the plant's energy gets added to the electrical energy being fed to the grid by other power plants. And the energy is simultaneously consumed by all of the loads drawing from the grid. Furthermore electric energy travels at light speed. So any disturbances can rapidly propagate throughout an electric grid. Disturbances to electric voltage and current frequency can damage electrical equipment that has been built to operate at specific voltages and frequencies. And electric outages, even momentary, can lead to large financial losses and or endanger lives. It is the job of electric system operators to keep electric supply balanced with demand, while ensuring there are sufficient system backups in place to keep the grid functioning if generators or grid components have to come off line or even fail. To accomplish this, the system operator must forecast the demand for electricity one day ahead. Schedule generation to meet this demand. Schedule backup or reserve generation along with other ancillary services. Schedule the use of transmission lines by various electric market participants. Share schedules with operators managing neighboring electric grids, so electric flow across grid interconnections can be managed. Adjust the generation & transmission resources to correct for minute by minute system imbalances. And fix the grid & restore electric power to it in the event there is an outage. Day-ahead forecasting of demand is done using models that draw upon historical demand data for that particular time of year, the next day's weather forecast and any information on upcoming business activity. These models will then be re-run the next day, while electricity is being in demanded, so that the forecast can be adjusted real time in response to the day's actual weather and other factors. With the day ahead forecast in hand, the system operator then schedules generation to meet anticipated demand, plus a certain level of unexpected demand or loss of generation. This back up generation represents the system's reserve requirements. A power flow model is then used to help determine a feasible schedule of which generators, and which transmission lines to use, to serve the demand of all the customers throughout the day. The goal of the modeling is to optimize the generation and transmission schedule on an hour by hour basis, so as to ensure good reliability while minimizing supply cost. If not enough generation or transmission is scheduled, supply will not meet demand. And if too much generation, and or transmission, is scheduled, more input energy to the power plant will be spent electrifying the grid than is necessary, possibly reducing grid reliability and for sure bringing about unnecessary wasted operation cost. Additional protective or ancillary services that the system service operator will contract include one automatic generation control to increase or reduce power generation is needed to meet short term fluctuations in customer load. Two, spinning reserves which are generators that are disconnected from the grid but are already turning at the same frequency and phase as the electric current on the grid. And so can be connected to the grid at a moment's notice if additional power is needed. Three, non-spinning reserves, which are generators that are not synchronized to the grid frequency but can be up and running and putting power onto the grid within 10 minutes if requested. Four, supplemental reserves, which are additional generators that need even more lead time before they can be connected to the grid, but which provide even more emergency back up power. And four, black start units, which are often diesel generators that provide power to power plants that have gone down and need electricity to get started again. System operators are responsible for managing their own electric grids, as well as for coordinating operations with the operators of adjacent interconnected grids. A system operator may be managing the grid of an investor owned utility, a municipal utility or a federal power agency. In certain instances the operator may be managing the grids of multiple utilities to the benefit of all the utilities. These particular types of system operators are known as independent system operators, or regional transmission operators. More concisely, they're known as ISOs or RTOs. System operators in different parts of the US and Canada coordinate their operations through eight regional reliability councils that make up the North American Electric Reliability Corporation or NERC. NERC sets the standards for operation reliability in North America. And the regional reliability councils implement these standards within their particular part of the North American electric grid. In fact, the North American electric grid consists of four separate regional transmission grids that generally operate independent of one another, but are interconnected, and so, back one another up. These four regional transmission grids are know as the Eastern, Western, Texas, and Quebec interconnections.
