Generation Interconnection Feasibility Study Report

Transcription

1 Project 76 Generation Interconnection Feasibility Study Report December 21, 2007 Electric Transmission Planning

2 Table of Contents Table of Contents... 2 Executive Summary... 3 Network Resource Interconnection Service Results... 3 Energy Resource Interconnection Service Results... 3 Definitions... 5 Network Resource... 5 Network Resource Interconnection Service... 5 Energy Resource Interconnection Service... 6 Generator and Interconnection Data... 7 Study Parameters... 8 Senior Queue Generator Assumptions... 8 Steady-State Power Flow Analysis... 9 Fault Duty Analysis Conclusions Required Mitigation Next Steps

3 Executive Summary NorthWestern Energy ( NWE ) has completed the initial Feasibility Study for Project 76 ( Generation Project ) near Ennis, MT. NWE studied your project as both a Network Resource Interconnection Service ( NRIS ) and an Energy Resource Interconnection Service ( ERIS ). The results of the Feasibility Study confirm that the addition of 75.6 MW interconnected to the NWE 100 kv transmission system near Bradley Creek substation is only feasible with system improvements. The findings included in this study do not assure the Interconnection Customer that the planned facility will be allowed to operate at full capacity under all operating conditions. Further and more detailed studies may reveal other operating constraints not revealed in the Feasibility Study. Network Resource Interconnection Service Results NRIS allows the Interconnection Customer to be designated as a Network Resource, up to the Large Generating Facility s full output, on the same basis as existing Network Resources interconnected to the Transmission Provider s Transmission System. NRIS does not in and of itself convey reservation of transmission service. Any network customer under the Tariff can utilize its network service under the Tariff to obtain delivery of electricity from the Generation Project in the same manner as it accesses Network Resources. The NRIS Feasibility Study identified thermal overloads on the following network elements: The 161/100 kv autotransformer located at Bradley Creek substation, The 100 kv line between Bradley Creek and the Generation Project, The 100 kv line between the Generation Project and Renova, and The 100 kv line between Renova and South Butte substation. A high level, non-binding cost estimate to interconnect your project is summarized in Table I. Table I. High Level, Non-Binding, Cost Estimate Substation $1,951,627 Relay $348,000 Communications $711,721 Metering $12,500 EMS $15,000 Upgrade 161/100 kv Transformer $1,250,000 Reconductor 100 kv line from Bradley Creek to Renova to Butte $7,500,000 Total $11,788,848 Energy Resource Interconnection Service Results ERIS allows the Interconnection Customer to connect the Large Generating Facility to the Transmission System and be eligible to deliver the Large Generating Facility s output using the existing firm or non-firm capacity of the Transmission System on an as available basis. ERIS 3

4 does not in and of itself convey any right to deliver electricity to any specific customer or Point of Delivery. This ERIS feasibility study is designed to answer two questions: I. What is the maximum allowed output to interconnect without additional network upgrades? Answer: The maximum output the Generation Project is allowed generate without additional network upgrades is 47 MW. II. What are the necessary upgrades to allow for full output of the Generation Project? Answer: The necessary upgrades to interconnect the full output of the Generation Project are the same as the NRIS study improvements. A high level, non-binding cost estimate to operate the Generation Project at full capacity is summarized in Table II. Table II. High Level, Non-Binding, Cost Estimate Substation $1,951,627 Relay $348,000 Communications $711,721 Metering $12,500 EMS $15,000 Upgrade 161/100 kv Transformer $1,250,000 Reconductor 100 kv line from Bradley Creek to Renova to Butte $7,500,000 Total $11,788,848 4

5 Definitions Network Resource Network Resource shall mean any designated generating resource owned, purchased, or leased by a network customer under the network integration transmission service tariff. Network Resources do not include any resource, or any portion thereof, that is committed for sale to third parties or otherwise cannot be called upon to meet the network customer's network load on a noninterruptible basis. Network Resource Interconnection Service NRIS shall mean an Interconnection Service that allows the Interconnection Customer to integrate its Large Generating Facility with the Transmission Provider s Transmission System (1) in a manner comparable to that in which the Transmission Provider integrates its generating facilities to serve native load customers; or (2) in an RTO or ISO with market based congestion management, in the same manner as all other Network Resources. Network Resource Interconnection Service in and of itself does not convey transmission service. NRIS allows the Generation Project to be designated by any network customer under the Tariff on NWE's Transmission System as a Network Resource, up to the Generation Project's full output, on the same basis as existing Network Resources interconnected to NWE's transmission system, and to be studied as a Network Resource on the assumption that such a designation will occur. Although NRIS does not convey a reservation of Transmission Service, any network customer under the Tariff can utilize its network service under the Tariff to obtain delivery of energy from the Generation Project in the same manner as it accesses Network Resources. A facility receiving NRIS may also be used to provide ancillary services after technical studies and/or periodic analyses are performed with respect to the Generation Project's ability to provide any applicable ancillary services, provided that such studies and analyses have been or would be required in connection with the provision of such ancillary services by any existing Network Resource. However, if the Generation Project s facility has not been designated as a Network Resource by any load, it cannot be required to provide ancillary services except to the extent such requirements extend to all generating facilities that are similarly situated. The provision of network integration transmission service or firm point-to-point transmission service may require additional studies and the construction of additional upgrades. Because such studies and upgrades would be associated with a request for delivery service under the Tariff, cost responsibility for the studies and upgrades would be in accordance with the Federal Energy Regulatory Commission s ( FERC ) policy for pricing transmission delivery services. NRIS does not necessarily provide the Generation Project with the capability to physically deliver the output of its facility to any particular load on NWE's transmission system without incurring congestion costs. In the event of transmission constraints on NWE's transmission system, the Generation Project s facility shall be subject to the applicable congestion management procedures in NWE's transmission system in the same manner as Network Resources. NWE will follow regional and sub regional congestion management procedures as they are developed. Once the Generation Project satisfies the requirements for obtaining NRIS, any future transmission service request for delivery from the Generation Project s facility within NWE's transmission system of any amount of capacity and/or energy, up to the amount initially studied, will not require that any additional studies be performed or that any further upgrades associated 5

6 with the Generation Project s facility be undertaken, regardless of whether or not the Generation Project s facility is ever designated by a network customer as a Network Resource and regardless of changes in ownership of the facility. However, the reduction or elimination of congestion or redispatch costs may require additional studies and the construction of additional upgrades. This philosophy is described in the FERC Order Nos. 2003, 2003-A, 2003-B and 2003-C, which govern interconnection of large generators to the transmission grid. The pro forma Large Generator Interconnection Procedures ( LGIP ) and Large Generator Interconnection Agreement ( LGIA ) required in those orders describe the philosophy that NWE used in performing the study work for the Generation Project. To the extent the Generation Project enters into an arrangement for long-term transmission service for deliveries from the facility outside of NWE's transmission system, such request may require additional studies and upgrades in order for NWE to grant the request. NorthWestern Energy is not required to provide certain ancillary services to transmission customers serving load outside of NorthWestern s control area. Energy Resource Interconnection Service Energy Resource Interconnection Service shall mean an interconnection service that allows the interconnection customer to connect its generating facility to the transmission provider's transmission system to be eligible to deliver the facility's electric output using the existing firm or nonfirm capacity of the transmission provider's transmission system on an as available basis. Energy Resource Interconnection Service in and of itself does not convey transmission service. Under Energy Resource Interconnection Service ( ERIS ), the Generation Project will be able to inject power from the facility into and deliver power across NWE s transmission system on an as available basis up to the amount of MW identified in the applicable stability and steady state studies to the extent the upgrades initially required to qualify for ERIS have been constructed. No transmission delivery service from the Generation Project is assured, but the Generation Project may obtain point-to-point transmission service, network integration transmission service, or be used for secondary network transmission service, pursuant to NWE s Tariff, up to the maximum output identified in the stability and steady state studies. In those instances, in order for the Generation Project to obtain the right to deliver or inject energy beyond the facility point of interconnection or to improve its ability to do so, transmission delivery service must be obtained pursuant to the provisions of NWE's Tariff. The Generation Project's ability to inject its output beyond the point of interconnection, therefore, will depend on the existing capacity of NWE's transmission system at such time as a Transmission Service Request ( TSR ) is made that would accommodate such delivery. The provision of firm point-to-point transmission service or network integration transmission service may require the construction of additional network upgrades. 6

7 Generator and Interconnection Data The proposed generator and interconnection data used in the studies was based on the information received from the Interconnection Customer. From the initial application, NWE identified the following project information. Project Name Project 76 Size (Rated) 75.6 MW total Location Approximately 5 miles North of Ennis, Madison County, MT Special Resources/Technology 36 Suzlon 2.1 MW Induction Wind Generators Proposed Commercial Operation Date December 31, 2008 Facilities Connection to the 100 kv transmission line approximately 5 miles North of Bradley Creek substation Assumptions o MW Output = 75.6 MW o o Scheduled Voltage (pu) = 1.0 at the Point of Interconnection The generator is assumed to have operational characteristics either through internal or external capabilities to operate throughout a power factor range of.95 leading to.95 lagging at the Point of Interconnection 7

8 Study Parameters In analyzing the Generation Project, NWE utilized PSS/E software to conduct the Feasibility Study with the proposed Generation Project. These studies connected the Generation Project to NWE s Transmission System in a computer model to simulate the interaction of the Generation Project with other resources and loads. All studies were conducted through a steady state powerflow analysis only. Two WECC base cases adjusted to include the NWE Transmission System detail representing 2010 light autumn and 2012 heavy summer loads were used for this study. Senior Queue Generator Assumptions In addition to existing generators, senior queue resources were also included in this study. (See Table III). Senior queued generation and existing generation dispatch were varied as needed to emulate stress on the system for various scenarios. In this study, Project 75 was studied nonsimultaneously with Project 76 (i.e. Project 75 was dispatched to 0 MW). Table III. Project Number Size (MW) Point of Interconnection Broadview Substation Colstrip Switchyard Wilsall-Shorey Road 230 kv Line Great Falls 230 kv Switchyard Martinsdale Substation Martinsdale Substation Billings Steam Plant Switchyard South Cut Bank - Conrad Auto 115 kv line Loweth - Two Dot 100 kv line kv line at Chester Rainbow Switchyard Choteau Substation Great Falls 230 kv Switchyard Wilsall-Shorey Road 230 kv Line Bradley Creek Substation Bradley Creek - Three Forks S. 100 kv line Bradley Creek - Three Forks S. 100 kv line 61 2 Phillipsburg - Anaconda 25 kv line kv line between Fairfield and Bole (total) 69 kv line near Sumatra (9 requests, 5 MW each) Cut Bank 115 kv Substation ASMI 161 kv Substation kv line appx 5 mi. N of Bradley Creek sub kv line appx 5 mi. N of Bradley Creek sub. 8

9 Steady-State Power Flow Analysis A review of the impact to the local area was conducted for each study. The local area impact study examined system normal operating conditions with all lines in service (i.e., N-0 conditions). Also, a limited number of critical local area single line outages (i.e., N-1 conditions) were studied. Power-flow computer simulations were done and a search of the study results for unacceptable thermal overload and voltage excursion was made for each power-flow study. Based on the study work, the following text summarizes those results. The addition of this project to NWE s Transmission System under N-0 conditions (all lines in service) causes an overload on the 100 kv line between Renova and Butte. The addition of this project to NWE s Transmission System under N-1 conditions (single line outages) causes several thermal overloads. No overloads existed before the addition of your project. A summary of thermal overloads is shown in Table IV. Table IV: Thermal Overloads Base case Outage Element Monitored Element % Overload % Overload Before Project After Project 2010 LA None: (N-0 condition) Renova--Butte 100 kv 55% 101% 2010 LA Gen. Project--Bradley Cr 100 kv Gen. Project--Renova 100 kv 2% 146% 2010 LA Gen. Project--Bradley Cr 100 kv Renova--Butte 100 kv 32% 111% 2010 LA Gen. Project--Har-Pony 100 kv Gen. Project--Bradley Cr 100 kv 0% 146% 2012 HS Coblestone--Bradley Cr 100 kv Bradley Cr 161/100 kv auto 25% 110% 2012 HS Gen Project--Har-Pony 100 kv Gen. Project--Bradley Cr 100 kv 2% 157% 2012 HS Gen. Project--Bradley Cr 100 kv Gen. Project--Renova 100 kv 0% 157% 9

10 Fault Duty Analysis When a fault occurs on a power line, protective relaying equipment detects the fault current flowing and signals associated circuit breakers to open. When the circuit breakers open they must be capable of interrupting the fault current. If the magnitude of fault current exceeds the interrupt rating of the circuit breakers, the fault may not be cleared, and damage to system equipment and voltage collapse may result. Busses at or near the point of interconnection of this project were faulted in a PSS/E model to determine the magnitude of fault current anticipated with this project in service. The results of this analysis suggest that standard circuit breaker fault duty ratings will not be exceeded. A more detailed analysis will be performed during the System Impact Study, and may reveal problems not discovered during the Feasibility Study. 10

11 Conclusions The results of this analysis confirm that the addition of 75.6 MW of generation interconnected to the NWE 100 kv transmission system near Bradley Creek substation is only feasible with system improvements. Required Mitigation In order to interconnect the Generation Project at full capacity, the following mitigation was identified. Replace the existing 161/100 kv, 30/40/50 MVA autotransformer at Bradley Creek Substation. Re-conductor the existing 100 kv line from Bradley Creek to Renova to Butte. This is not a request for transmission service. The findings included in this study do not assure the Interconnection Customer that the planned facility will be allowed to operate at full capacity under all operating conditions. Further and more detailed studies may reveal other operating constraints not revealed in the Feasibility Study. Next Steps NWE will be scheduling a meeting to discuss the findings of the Feasibility Study with the Interconnection Customer. If, after the meeting, the Interconnection Customer wishes to continue with the project, a System Impact Study specific to the project will be required to further determine the requirement for the interconnection. The System Impact Study is a much more detailed study that includes transient stability, fault duty, post transient, and comprehensive outage studies (i.e., N-1 and N-2). It is possible that the System Impact Study will identify concerns that need to be addressed in order to interconnect the Generation Project or it will modify the results expressed herein. This study does not constitute a request for transmission service. The study examined the physics of the electrical system and does not imply that you will receive any transmission required to deliver the generation output to load. You must follow the procedures described in the transmission tariff available on ( to request and/or receive transmission service. 11