NorthWestern Energy’s Revised
Open Access Transmission Tariff
Filed with FERC August 2004
Reason for Filing a Revised Tariff
The main reason NorthWestern Energy is filing a revised Open Access Transmission Tariff (OATT or Tariff) is to add a new Schedule 9, Generation Imbalance Service, which is intended to address imbalances between the amount of energy that is scheduled for transmission from generator and the amount of energy actually received from that generator. NorthWestern Energy has a need for this service because many new generation projects have been proposed within its service territory and Generation Imbalance Service was removed from the final pro forma Large Generation Interconnection Agreement and is not expected to be included as a service in the Small Generation Interconnection Agreement, thus requiring NorthWestern Energy to address this service in its OATT.
Brief Description of the Generation Imbalance Service Rates, Terms and Conditions
The rates, terms and conditions set forth in Schedule 9 are substantially identical to similar services that the Commission has previously found to be consistent with or superior to the provisions of the pro forma OATT.
For purposes of determining the charges for Generation Imbalance Service, NorthWestern Energy has established a deviation band which covers imbalances within +/- five percent (5%) of the scheduled transaction (if the imbalance during any hour is 2 MW or less, it will be deemed within the deviation band). A Negative Imbalance results if the amount of energy received from the generator is less than the amount scheduled and a Positive Imbalance results if the amount of energy received from the generator is greater than the amount scheduled. For Negative Imbalances within the deviation band, the generator will pay NorthWestern Energy 100 percent of the Market Power Price for the energy associated with the imbalance; for Negative Imbalances outside the deviation band, the generator pays NorthWestern Energy 110 percent of the Market Power Price for the energy associated with the imbalance. For Positive Imbalances within the deviation band, NorthWestern Energy will pay the generator 100 percent of the Market Power Price for the energy associated with the imbalance and for Positive Imbalances outside the deviation band, NorthWestern Energy will pay the generator 90 percent of the Market Power Price for the energy associated with the imbalance. The Market Power Price is defined as NorthWestern Energy’s “actual cost, which is the hourly weighted average cost of its contracted system balancing and load following energy costs.” Substantially similar rates have been approved by the Commission.
Exceptions to Applicability of Schedule 9
There are three exceptions to the applicability of Schedule 9: (1) if a generation-to-schedule imbalance is offset by a schedule-to-load imbalance for the same transaction that is covered by a charge under Schedule 4 (Energy Imbalance Service), then no charge will be assessed under Schedule 9 to the extent of the offset; (2) no Generation Imbalance Service charge will be assessed if the imbalance occurs because the generator is providing frequency control service at the request of NorthWestern Energy; and (3) no Generation Imbalance Service charge will be assessed if the imbalance occurs because the generator is providing operating (spinning or supplemental) reserves at the request of NorthWestern Energy.
Other Tariff Changes Besides the Addition of the Generation Imbalance Service Schedule
1. Energy Imbalance Service
NorthWestern Energy proposes to amend the definition of Market Power Price in Schedule 4 to reflect the actual cost incurred by NorthWestern Energy to provide the service, to confirm its current practice of calculating Market Power Price and; as a result, also to be consistent with the definition of Market Power Price proposed in Schedule 9, Generation Imbalance Service.
2. Order No. 2003-A Compliance Filing
In FERC Order 2003-a, FERC stated that when a Transmission Provider modified its Tariff, as NorthWestern Energy is doing to incorporate Generation Imbalance Service, it must make a ministerial filing incorporating the Large Generation Interconnection Procedures, Large Generation Interconnection Agreement, and the other related documents in its Tariff.
NorthWestern Energy proposed certain modifications to the LGIA, which are detailed in its FERC filing transmittal letter.
Questions
Please direct questions to:
Marc E. Donaldson, P.E.
Manager, Electric Transmission Scheduling
NorthWestern Energy
40 E. Broadway
Butte, MT 59701
Phone: 406-497-4717
Fax: 406-497-2054
Cell: 406-490-8249
Email: