Ancilliary and Control Area Services (ACS) 101

    Ancilliary Services Map
    • ACS are services necessary to support the transmission of energy from resources to loads while maintaining reliable operation of BPA’s Balancing Authority Area in accordance with Good Utility Practice. 
    • BPA, as the Transmission Provider, is required to provide ACS under the pro forma tariff.
    • Transmission customers are required to purchase certain ACS from BPA under the pro forma tariff.  
    • There are additional ACS that the transmission customer must either purchase from BPA, or self-supply through a customer’s own resources or from a third-party accordingly, as required under the pro forma tariff. 

    What is the full list of ACS services?

    • Schedule 1 - Scheduling, System Control, and Dispatch
    • Schedule 2 - Reactive Supply and Voltage Control from Generation Sources
    • Schedule 3 - Regulation and Frequency Response
    • Schedule 4 - Energy Imbalance
    • Schedule 5 - Operating Reserve (Spinning)
    • Schedule 6 - Operating Reserve (Supplemental)
    • Schedule 9 - Generation Imbalance
    • Schedule 10 - Capacity for Generator Balancing (VERBS/VERS & DERBS/DERS)
    • Schedule 11 - Real Power Losses (Transmission Losses)

    BPA is also providing a quick overview of its Balancing Reserves.  Schedules 3, 4, 9 & 10 cover BPA's offered ACS services for Balancing Reserves.  A similar overview on Operating Reserves is coming soon!

Who will need What Ancillary Services?
  • Scheduling on the transmission system will need schedules 1, 2 and 11
  • Load will need schedules 3 and 4
  • Generation will need schedules 9 and 10
  • Both Generation and Load will need schedules 5 and 6
  • EIM participants will need schedules 4e and/or 9e