Generation Interconnection Feasibility Study Report

Transcription

1 Project #169 Generation Interconnection Feasibility Study Report 7/2/2014 Regional Electric Transmission Planning

2 TABLE OF CONTENTS Executive Summary... 3 Generator and Interconnection Data... 5 Study Parameters... 6 Steady-State Power Flow Analysis... 6 Fault Duty Analysis... 7 Conclusions... 8 Required Mitigation... 8 Next Steps... 8 Appendix: One-Line Drawing

3 Executive Summary NorthWestern Energy (NWE) has completed the Feasibility Study for Project 169 near the Yellowtail Substation in southeast Montana. NWE studied this project as a small generation energy resource (ERIS). The results of the Feasibility Study confirm that the addition of 10 MW interconnected to the NWE 230 kv Yellowtail-Steamplant 230 kv transmission line, approximately 0.5 miles north of PacifiCorp s Yellowtail substation, is feasible under normal operating conditions (i.e., all lines in service) without any additional network upgrades beyond the facilities needed for interconnection. The findings included in this study do not assure the Interconnection Customer (Customer) that the planned facility will be allowed to operate at full capacity under all operating conditions. Generation curtailment may be required under certain outage conditions. More detailed studies may reveal other operating constraints not seen in the Feasibility Study. The feasibility study identified no adverse impacts due to the Generation Project under normal operating conditions. Since the Customer did not specify either an exact point of interconnection (POI) or a specific turbine, NWE used professional engineering judgment to model this interconnection request. In the interconnection request, the Customer states, Yellowtail substation is approximately 1.25 miles from the proposed project site. NWE does not own the Yellowtail substation or the nearby Big Horn substation and, as a result, the study could not use either substation as the point of interconnection (POI). NWE owns the 230 kv line between Yellowtail and the Billings Steam Plant, therefore, the project tap was assumed on that line near the proposed project site. NWE modeled the Customer s point of interconnection as a new substation approximately a half mile north of the Yellowtail substation on NWE s 230 kv transmission line. Because the request entails a new substation on a 230 kv line, there will be a need for redundant communications as well as a temporary bypass (shoefly) line to keep the 230 kv line in service. The 230 kv line of interest is on a major transmission path, as defined by the Western Electricity Coordinating Council, and the temporary bypass allows NWE to maintain flows on that line during the construction of the substation. Once construction of the substation has been completed, the temporary bypass will be removed. The Customer did not specify a turbine, therefore, this report will not address the results of fault duty analysis. The Customer will be required to select a turbine and point of interconnection before the System Impact Study (SIS) can begin. The SIS is a detailed technical analysis, and the fault duty will be addressed in this study. 3

4 A high level, non-binding cost estimate to interconnect the Generation Project is summarized in Table I. Table 1: High Level Non Binding Estimate of Interconnection Costs Department Estimate Notes Transmission $750,000 Includes the construction and removal of the temporary 230 kv bypass. Substation $2,270,000 New substation on 230 kv line. Lands/Permitting $43,900 Estimate depends on substation location (private or public land). Environmental issues cannot be addressed until specific POI has been selected. Relay $400,000 System protection. Communications $15,000 NWE will install and lease a satellite connection. The Customer must arrange for the circuits. Ongoing monthly costs are estimated at $130/month; this provides a connection from EMS to a supervisory at the substation. Metering $14,000 EMS $12,000 Generation modeling/licensing, and system scada point licensing Total $3,504,900 4

5 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 169 Size (Rated) 10 MW total Location near Fort Smith, MT Special Resources/Technology -- Unspecified Proposed Commercial Operation Date 2017 Facilities NWE 230 kv substation approximately one half mile north of the Yellowtail substation on the 230 kv Yellowtail-Steamplant line. Assumptions o MW Output = 10 MW o Scheduled Voltage (p.u.) = 1.00 at the Point of Interconnection o The generator was modeled to have operational characteristics of 0.95 leading to 0.95 lagging power factor ranges. 5

6 Study Parameters In analyzing the Generation Project, NWE utilized PSS/E software to conduct the Feasibility Study for the proposed Generation Project. These studies simulated the connection of the Generation Project to NWE s Transmission System in a computer model to study the interaction of the Generation Project with other resources and loads. All studies were conducted through a steady state power-flow analysis only. Two WECC base cases adjusted to include the NWE Transmission System detail representing 2014 light summer and 2014 heavy summer load profiles were used for this study. Steady-State Power Flow Analysis A review of the impact to the local area was conducted for this feasibility study. The local area impact study examined system normal operating conditions with all lines in service (i.e., N-0 conditions) as well as a limited number of critical local area single line outages (i.e., N-1 conditions). Power-flow 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 causes no adverse effects. The addition of this project to NWE s Transmission System under N-1 conditions does not cause any voltage or thermal violations. No system mitigation is required at this time. 6

7 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. Because the Customer did not provide a specific turbine, NWE is unable to conduct a Fault Duty Analysis in the Feasibility Study. The Customer will be required to specify a turbine for the System Impact Study where the Fault Duty Analysis for this project will be conducted. 7

8 Conclusions The results of this analysis confirm that the addition of 10 MW of generation interconnected to the NWE 230 kv transmission system in the Yellowtail-Steamplant 230 kv segment approximately 0.5 miles north of the Yellowtail substation, is feasible under normal operating conditions without any additional network upgrades beyond those necessary for interconnection. At this time, no system upgrades beyond the facilities required for interconnection are needed in order to interconnect the full output of the Generation Project under system normal operating conditions. Required Mitigation Since the generation project caused no adverse effects, no mitigation is required at this time for interconnection of the generation project. Curtailment of the project may be required under certain outage conditions. 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) and will require identification of generator turbine type and point of interconnection. It is possible that the System Impact Study could identify concerns which may require mitigation in order to interconnect the Generation Project. This study does not constitute a request for transmission service. The study examined the physics of the electrical system and does not imply that the Customer will receive any transmission required to deliver the generation output to load. The Customer must follow the procedures described in the transmission tariff available on ( to request and/or receive transmission service. 8

9 Appendix: One-Line Drawing Figure 1: One-Line Drawing of Interconnection Project