Local Transmission Plan
Results of NorthWestern Energy’s Transmission
2-Year Planning Cycle
January 1, 2008 to December 31, 2009
Final 12-22-09
Electric Transmission Planning
Table of Contents
Executive Summary
NWMT Transmission System Overview
Meeting FERC 890 requirements
Public Input
Local
TRANSAC
Public Meetings
Sub-Regional
Regional
WECC Annual Study Program
Economic Planning Study Cycles
2008 Economic Planning Study Cycle
2008 Economic Planning Study Results for Montana Wind & Wires
Glacier & Toole County
Wheatland & Judith Basin County
Park/Sweet Grass/Stillwater County
2009 Economic Planning Study Cycle
Planning Methodology
NWMT Local Transmission Planning Methodology
Reliability Criteria
NWMT Internal Reliability Criteria
Steady State and Post Fault Voltage Criteria for 230 kV and Below
Steady State Voltage Criteria for 500 kV
Thermal Ratings
General Minimum Equipment Specifications
Process to implement Methodology
Goal
Planning Scenarios
Technical Study
Developing the Load Forecast
Load Forecast
State of the System Study
State of the System Summary of Findings prior to Mitigation
Prioritizing Critical Problems
Bozeman Area: Jackrabbit 161/50 kV Auto
Missoula/Hamilton Area: Missoula #4 100/69 kV Auto Transformers
Great Falls Area: Rainbow – GF Northeast 100 kV Line
Billings Area: Steam Plant 230 kV Switchyard
Columbus – Absarokee – Stillwater Area 50 kV and 100 kV Systems
Butte/Anaconda Area: Mill Creek Substation 161 kV Bus
Bozeman Area: Ennis – Big Sky 69 kV System
Columbus Area: Columbus Rapelje – Alkali Creek 161 kV Line
Missoula/Hamilton Area: Missoula – Hamilton Heights 161 kV Lines
Decision
Decision Rule
Uncertainty
Recommendation Summary
Figures
Figure 1: Montana Paths
Figure 2: Internal paths & External paths
Figure 3: Local and Sub-Regional Planning
Figure 4: Expected Economic Study Process
Figure 5 – Study Cycle Coordination
Tables
Table 1 – NWMT Economic Planning Study
Table 2 – Planning Methodology
Table 3 – Maximum Upper Voltage Criterion
Table 4 – Minimum allowable Percent Voltage at NWMT Unregulated Load-Serving Bus
Table 5 - T&S Equipment: General Minimum Specifications
Table 6 – Study Scenarios
Table 7 – Control Area Load Forecast with DSM
Table 8 – Estimated peak load temperature sensitivity
Table 9 – Peak Load Forecast
Table 10 - Highest Priority System Matrix
Table 11 - Decision Rule Matrix
Table 12 - Recommendation Summary
Attachments
Attachment A - TRANSAC Charter
Attachment B – Transmission Advisory Committee (TRANSAC) Meetings
Attachment C – Economic Study Requests 2008
Executive Summary
NorthWestern Energy’s (NWMT) methodology, process and criteria are used to evaluate the electric transmission system, ensuring that system reliability is maintained into the future. NWMT’s followed the Business practice, methodology, criteria and process outlined in our FERC Order 890 Attachment K filing.[1]
Reliability, by definition, examines the adequacy and security of the electric transmission system. Consistent application of the methodology, criteria, and process for all balancing area customers (i.e., retail, network and point-to-point) information is ensured through the openness and transparency of NWMT’s process. All customers are treated on an equal and comparable basis as NWMT’s transmission system planning process is designed to be transparent, open and understandable. NWMT’s methodology is intended to define operating conditions that fail to meet reliability criteria and then identify solutions (e.g., transmission and non-transmission[2]) that solve the problem.
NorthWestern Energy has performed a multi-seasonal, multi-year study that was designed to examine our system’s reliability under normal operating conditions, and all single and credible multiple outage conditions. This study work has created a benchmark for future biennial studies to be compared against. This comparison will provide knowledge on how the system is changing over time. Given the results, NWMT designed mitigation plans that will resolve the identified problems, starting with the most critical first.
To ensure that the NWMT’s Transmission Planning process was open and transparent throughout the entire process, a Transmission Advisory Committee (TRANSAC) was formed. TRANSAC is an advisory stakeholder committee that meets regularly with NWMT to provide input and comments during the planning stages of NWMT’s Local Transmission Plan. Please see Attachment A - TRANSAC Charter for an outline of TRANSAC’s purpose and Attachment B – Transmission Advisory Committee (TRANSAC) for an outline of TRANSAC’s involvement with the development of this plan.
This document walks you through NWMT’s efforts to develop the Local Transmission Plan that addresses reliability by examining the adequacy and security of the electric transmission system while following our business practices, methodology, criteria and process. The findings of NWMT’s efforts include the following:
In the near term no low voltage or thermal problems occur under normal operating conditions.
Without planned mitigation, there are a limited number of outages that may cause voltage and thermal problems, especially on lower voltage systems.
The majority of thermal problems observed are transformer capacity related rather than line capacity, which can be mitigated through upgrades or operational means.
As load grows, substation related outages are becoming more critical without mitigation.
No outages result in uncontrolled cascading.
No transient stability problems were observed.
With load growth over time thermal loads and related problems grow and voltages decline without mitigation.
NWMT Transmission System Overview
NWMT’s local transmission system provides regulated electric transmission services to approximately 300,000 electric customers. NWMT’s electric transmission system consists of approximately 7,000 miles of transmission lines and associated terminal facilities. NWMT is registered as a Balancing Authority, Planning Authority and Transmission Planner. Effective January 1, 2009, 222 megawatts of electricity from the coal-fired unit in southeastern Montana was rate based. The decision makes Colstrip Unit 4 the foundation of NorthWestern Energy’s efforts to become a vertically integrated utility in Montana.
The transmission system, with voltage levels ranging from 50,000 to 500,000 volts, serves an area of 97,540 square miles, which is equivalent to two-thirds of Montana. The 500 kV transmission system is primarily used to move power from Colstrip in eastern Montana to the Northwest. NWMT’s transmission system has interconnections to five major transmission systems[3] located in the Western Electricity Coordinating Council (“WECC”) area and one DC interconnection to a system that connects with the Mid-Continent Area Power Pool (“MAPP”) region.
The following two Figures display the internal and external paths with the associated non-simultaneous path ratings.
Figure 1: Montana Paths
Figure 2: Internal paths & External paths
Meeting FERC 890 requirements
The Federal Energy Regulatory Commission (FERC) issued its Order No. 890 on February 16, 2007 (Order). The Order provided amendments to the regulations and the pro forma Open Access Transmission Tariff (OATT) adopted in Orders 888 and 889. The Order became effective May 14, 2007. The order requires a more inclusive transmission planning process incorporating the following nine principles: (1) Coordination, (2) Openness, (3) Transparency, (4) Information exchange, (5) Comparability, (6) Dispute resolution, (7) Regional participation, (8) Economic Planning Studies, and (9) Cost allocation for new projects[4]. The documents that outline NorthWestern Energy’s efforts, business practices and support FERC Order No. 890 are listed in a single document called “Attachment K Business Practice Links” and is posted on NWMT OASIS website as follows:
NorthWestern Energy met FERC Order 890 requirements by following our Attachment K Business Practice4 and producing this document. Briefly, we met the requirements for the nine principles as follows:
Coordination and Openness are met through 1) a public process to allow two-way communication with stakeholders and interested parties throughout our transmission planning process; and 2) coordinating our plan with the Northern Tier Transmission Group (NTTG) throughout their sub-regional planning process; and 3) coordination of our plan with the Western Electricity Coordinating Council’s (WECC) regional planning organizations. (See the Public Input section of this document.)
Transparency is met by disclosing our basic methodology, criteria, process and data used to develop its local transmission plan[5] and requesting input through the public process (TRANSAC meetings). (See the Public Input section of this document.)
Information Exchange is met through data requests to our Load Serving Entities (LSE) and/or customer (e.g., network and point-to-point)[6] and once data is combined NorthWestern Energy submits to WECC the annual WECC Loads and Resources data request and the WECC Power Supply Assessment data request.
Comparability is met by combining the forecast load and generation information received from the customers with NWMT’s transmission line and equipment data and including that data, as appropriate in the database used in the reliability assessment.
Dispute Resolution is met through NWMT’s dispute resolution process and by following the NTTG and WECC dispute processes for sub-regional and regional planning disputes.[7]
Regional Participation is met by NWMT’s active membership in the Northern Tier Transmission Group (NTTG), and the WECC Transmission Expansion Policy and Planning Committee (WECC TEPPC). Also, this local transmission plan will be shared with interconnected transmission systems, sub-regions and region entities as required or requested.
Economic Planning Studies is met through the Economic Planning Process. One economic study was completed in 2008 and no economic study requests were received in 2009. (See the Economic Planning Study Cycles section of this document.)
Cost Allocation for New Projects is met by following NWMT’s business practice “Local Cost Allocation Methodology Outside of OATT”[8].
Public Input
Local
TRANSAC
The concept of a Transmission Advisory Committee (TRANSAC) was formulated at an open public meeting held May 3, 2007 to present and review the development of a strawman NorthWestern Energy’s initial proposed response to FERC Order 890. This effort developed into our “OASIS Attachment K Business Practice” and addresses openness, transparency and ways for the public to provide input[9]. The purpose of TRANSAC is to provide an open transparent forum whereby electric transmission stakeholders can comment and provide advice to NorthWestern Energy during its electric transmission planning process. TRANSAC membership is open to anyone and is established through self-nomination. Standards of Conduct and Critical Energy Infrastructure information are followed and discussion at these meetings is limited to NWMT electric transmission planning issues. TRANSAC is not a decision making body, and does not make decisions as a group, it provides comment and advice only. Please see Attachment A - TRANSAC Charter for an outline of membership, process, member responsibilities, contacts and confidentiality.
As of 12/16/09 there are 61 individuals on the stakeholders distribution list that comprise of representatives from such organizations as Bonneville Power Administration, PPL Montana, Idaho Power Company, Large Industrials, Generation Interconnects, Western Area Power Administration (WAPA), Columbia Grid, Puget Sound Energy, NorthWestern Energy, Avista, Montana State Department of Commerce, Montana Consumer Council, MATL, Montana Public Service Commission, MT Department of Environmental Quality (DEQ), Yellowstone Valley Electric, Beartooth Electric, Missoula Electric Coop and Ravalli County Electric. Notices of meeting related postings on the OASIS and meeting related material were sent to the distribution list on a regular basis. All individuals were invited to attend or join in the TRANSAC meetings and NorthWestern Energy solicited their input throughout the planning process.
The development of the Electric Transmission System Plan was discussed with TRANSAC members through a series of meetings and conference calls that were announced and posted on our OASIS site[10]. Six meetings were held in 2007, eight meetings or conference calls in 2008, and five meetings or conference calls in 2009. The postings on the OASIS site include the meeting announcements, agendas, meeting materials and meeting summaries. For a summary of meeting dates and topics discussed please see Attachment B – Transmission Advisory Committee (TRANSAC).
Public Meetings
Meetings for the general public during the two-year planning cycle were discussed at TRANSAC meetings in December 2007 and January 2008. Based on advice at those meetings, NorthWestern Energy decided that the first public meeting should be after the State of the System study so that the results of the current and future state of our transmission system could be presented. Initial preliminary results of the State of the System study were presented to TRANSAC with updates and discussion of public meetings at the November 2008, December 2008, January 2009, March 2009 and June 2009 TRANSAC meetings. Based on the discussions NorthWestern Energy chose to hold public meetings at the Billings and Missoula NorthWestern Energy Division offices in the fall of 2009. Billings and Missoula were chosen because most new system upgrades found to be necessary through this planning process occurred in the Billings and Missoula areas. Announcements for the meetings were posted on the OASIS at least 30 days prior to the meeting dates and personal invitation letters were sent to the local rural electric cooperatives. There were 10 participants at the Billings meeting held September 22, 2009including two journalists and representatives from Yellowstone Valley Electric, Beartooth Electric, Western Area Power Administration (WAPA), Rosebud Operations (BGI) and a private engineering/consultant firm. There were 6 participants at the Missoula meeting held September 24, 2009including a TRANSAC member and representatives from Missoula Electric Coop and Ravalli County Electric. The results of the two meetings included adding three new members to TRANSAC.
Sub-Regional
In the sub-regional context, NWMT is an active member of the Northern Tier Transmission Group (“NTTG”) and uses the NTTG process for sub-regional planning, coordination with adjacent sub-regional groups and other planning entities, and proposals to WECC Transmission Expansion Policy and Planning Committee (“WECC TEPPC”) for regional planning. NTTG develops a coordinated Sub-Regional Transmission Plan and responds to requests for Economic Planning Studies.
The NTTG Planning Agreement and the NTTG Planning Charter govern the relationship between NWMT local transmission planning and the NTTG sub-regional transmission planning. These documents are available on NWMT’s OASIS website. The FERC 890 principle obligations are met by NTTG providing an open forum to coordinate transmission plans of its members with those of other sub-regional transmission groups within the Region. NTTG also has a cost allocation committee that determines cost allocations for qualifying system additions where agreement on cost allocation has not been reached.
NWMT participates in the NTTG planning process to ensure data and assumptions are consistent and that we are properly represented in the NTTG sub-regional plan. The NTTG sub-regional plan is coordinated by NTTG with neighboring sub-regional entities (e.g., Columbia Grid). Once the NTTG’s sub-regional plan is developed, it is shared with WECC, and the WECC process coordinates the NTTG sub-regional plan with all of the other sub-regional plans within the WECC region.
NWMT coordinates and submits its data, assumptions and local transmission plan to NTTG for inclusion in the NTTG sub-regional transmission plan. NTTG coordinates with other sub-regional planning processes within the northwest.
An example of the data and plan coordination for this process is shown in Figure 3: Local and Sub-Regional Planning. As the figure shows, data and plan information is coordinated between the local planning process, the NTTG sub-regional planning process[11] and the WECC regional planning process.
Figure 3: Local and Sub-Regional Planning
Regional
WECC Annual Study Program
In addition to NWMT’s own local transmission planning study, NWMT participates in the WECC Annual Study Program. This program examines the reliability of electric transmission lines that are instrumental in moving electricity across the NWMT system from sources of supply inside and outside Montana to markets inside and outside Montana. These lines generally range in size from 100 kV through 500 kV. A detailed simulation model[12] is used for steady state and dynamic event analysis that assesses electric transmission stability before and after a loss of a critical electrical element (e.g., line). NWMT provides its local transmission plan, data and assumptions to WECC regional committees[13] that are responsible for building databases. Regional committees use these data for database development, load and resource assessments, operating studies and planning studies.
Two types of study assessments are conducted – Operating Transfer Capability (“OTC”) studies and Bulk System Planning Studies. The distinction between these studies is that the OTC study establishes the next season’s maximum transfer capacity for selected electric transmission path and the planning studies evaluate the bulk transmission system’s adequacy and security 2-10 years into the future. The Annual Study Program requires that each year approximately ten detailed studies be conducted to assess bulk electric transmission reliability. The mix of operating and planning studies varies each year.
When conducting a seasonal OTC study, NWMT follows the WECC policy of using a critical outage for a load condition and generation pattern defined by WECC to establish the OTC that meets reliability criteria. The specific load and generation patterns may include heavy winter or summer loads with maximum thermal generation and critical hydro conditions and light spring loads with maximum generation. The outages that are of interest may include single or double line loss of the critical lines. After completing a study, NWMT looks within its system and outside its system for unacceptable voltage concerns, overloaded electrical equipment and frequency excursion. The equipment examined includes, but is not limited to, generators, transmission lines, transformers, series capacitors, wave-traps, circuit switchers, and circuit breakers. Other electrical equipment on the system may limit the transfer of power through a system; therefore, they need to be considered when conducting studies. Voltage levels are reviewed to make sure that the steady state, post-fault and transient voltage performances comply with all criteria. NWMT checks for unacceptable equipment thermal loading, voltage swings and positive damping after transient excursions on a system-wide basis. See the Criteria section of this document for criteria requirements.