Ancillary Services

Ancillary services can be thought of as the overhead costs needed to maintain the functionality and reliability of the power grid system. This includes balancing the flow of electricity as it moves across the transmission system from generators to the retail consumers. Balancing the flow of energy across the power grid system consists of matching supply and demand. It’s possible for segments of the power system to be overloaded which can lead to overheating, line breakage, and power outages.

One of the important functions of ancillary services is to have a defined frequency range to prevent the system from collapsing. The Pennsylvania, Jersey, Maryland Power Pool (PJM) is a regional transmission organization (RTO) that coordinates the movement of wholesale electricity in 13 states including the District of Columbia. PJM maintains the power lines with a frequency of 60 Hertz. Two important ancillary services to help balance supply and demand while maintaining the defined frequency pertains to regulation and reserves.

Regulation – This is the ability to control the output of generation or consumption as a result of an automated response. This method is achieved by market-based compensation to the resources that can make adjustments. Regulation helps balance supply and demand by correcting the imbalances between scheduled generation and real-time consumption.

Reserves – This refers to energy assets that are currently not being used but can be utilized in response to a loss of power generation. PJM separates the reserves into two categories that include primary and supplemental.

• Primary reserves: This is the amount of power that can be received in 10 minutes from generators synchronized to the power grid or offline. This also includes certain loads used for the demand-side response that can be removed from the grid.
• Supplemental reserves: This refers to the amount of power that can be received in 10 to 30 minutes. This power can come from the same resources as primary reserves.