Balancing authorities are responsible for the performance of the electric system is to ensure that at every moment of time there is sufficient generation to reliably supply the customer requirements and all associated delivery system losses. The process is complicated by the fact that the customer load changes continuously and, therefore, the generation must adjust immediately, either up or down, to accommodate the load change. Since electric power cannot be stored, the generation change must be accomplished by a physical adjustment of the equipment generating the electricity.
The Balancing Authority Areas vary greatly in both geographic size and the amount of generation/ load they control.
With this information, the Balancing Authorities can compare the total scheduled interchange into or out of the control area with the actual interchange. If the flow into the area exceeds the schedule for that time period, internal generation must be increased. Conversely, if the net flow is below the schedule, generation within the area must be reduced. Operationally, this is an ongoing process conducted every few seconds. Since these adjustments are going on simultaneously in all balancing areas, the adjustments balance out.
Each Balancing Authority also participates in maintaining the average system frequency at 50 or 60 hertz. The system frequency can deviate from normal when a large generating unit or block of load is lost. In addition to adjustments made because of variations of tie flows from schedule, another adjustment is made to correct frequency deviations. Each Balancing Authority is required to have an adjustment factor related to frequency in its control logic. The term is called the tie-line frequency bias (expressed in mW/0.1 Hz).
Additionally, since the control process is responsive, there can be a drift in average system frequency, which, in turn, affects the accuracy of any electric clocks. This variation is monitored and for a period of time the target frequency reference is adjusted to produce the required compensation. This process is called time error correction.
With the restructuring of the industry; the emergence of merchant power plant owners; the development of ISOs, RTOs, and for-profit transmission companies; and the implementation of retail access in some regulatory jurisdictions, assigning all reliability responsibilities to balancing authorities made the job of defining and applying standards more and more complicated. This was further complicated since some balancing areas are acting as transmission service providers.
The ongoing adjustments to generation levels within each balancing area are, of course, done by computer-based control systems that send signals to generators that provide needed adjustments (i.e., regulation), either up or down.
The Balancing Authority Areas vary greatly in both geographic size and the amount of generation/ load they control.
AREA CONTROL
Each Balancing Authority is responsible for maintaining its own load/generation balance, including its scheduled interchange, either purchases or sales. A Balancing Authority can consist of a generator or group of generators, an individual company, or a portion of a company or a group of companies, providing that it meets certain certification criteria. Since minute-by-minute customer load changes are not known in advance, a system has been developed whereby generation changes are made in response to load changes. This system is based on the concept of the area control error. The sum of the internal generation within a Balancing Area and the net flow on its interties is equal to the customer load and all transmission losses within the area. The net power flow into/out of the area should be equal to the net of all transactions between parties in the area and parties outside the area. To determine the net schedule transactions, the various commercial interests that are within the area are required to notify the Balancing Authority personnel (via the Interchange Coordinator) of their bilateral contractual arrangements on an ongoing basis for either sales or purchases of electricity with entities outside the area’s boundaries. Additionally, neighboring operating entities engaged in transactions that will cause power to flow through the Balancing Area are required to notify the Balancing Authority (through the Interchange Authority) and to make provision for the attendant transmission losses.With this information, the Balancing Authorities can compare the total scheduled interchange into or out of the control area with the actual interchange. If the flow into the area exceeds the schedule for that time period, internal generation must be increased. Conversely, if the net flow is below the schedule, generation within the area must be reduced. Operationally, this is an ongoing process conducted every few seconds. Since these adjustments are going on simultaneously in all balancing areas, the adjustments balance out.
Each Balancing Authority also participates in maintaining the average system frequency at 50 or 60 hertz. The system frequency can deviate from normal when a large generating unit or block of load is lost. In addition to adjustments made because of variations of tie flows from schedule, another adjustment is made to correct frequency deviations. Each Balancing Authority is required to have an adjustment factor related to frequency in its control logic. The term is called the tie-line frequency bias (expressed in mW/0.1 Hz).
Additionally, since the control process is responsive, there can be a drift in average system frequency, which, in turn, affects the accuracy of any electric clocks. This variation is monitored and for a period of time the target frequency reference is adjusted to produce the required compensation. This process is called time error correction.
OPERATING RESERVES
Each Balancing Authority must provide operating reserves to restore its tie flows to schedule within 15 minutes following the loss of a generator within the area. Operating reserves consist of spinning and non-spinning reserves. Spinning reserve is generation that is synchronized and available to supply incremental load in a specified time period. Non-spinning reserve is not synchronized but can be made available within a short period of time. Interruptible load disconnection and coordinated adjustments to interchange schedules can be considered as part of operating reserve.With the restructuring of the industry; the emergence of merchant power plant owners; the development of ISOs, RTOs, and for-profit transmission companies; and the implementation of retail access in some regulatory jurisdictions, assigning all reliability responsibilities to balancing authorities made the job of defining and applying standards more and more complicated. This was further complicated since some balancing areas are acting as transmission service providers.
The ongoing adjustments to generation levels within each balancing area are, of course, done by computer-based control systems that send signals to generators that provide needed adjustments (i.e., regulation), either up or down.
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