Apex - RTP Transmission Project
Population and energy usage continue to increase in the Triangle region, and plans indicate that significant additional development is expected for the region. Today, the electric transmission system that serves the region is constrained under certain conditions.
Duke Energy Progress’ continuous assessment of electric system requirements had earlier identified the need for enhancements to help ensure a continued reliable supply of electric service to homes and businesses. Portions of the western Wake County transmission project were announced and commenced in 2001, and some transmission improvements have already occurred in this corridor.
Late in 2006, the N.C. Transmission Planning Collaborative issued a preliminary report that confirmed the need for additional improvements and upgrades in this region to enhance electric system reliability and to promote enhanced transmission access across the state. The transmission study group included representatives from Duke Energy Progress, Duke Energy, the state's electric cooperatives, municipally owned electric systems and an independent third party. The changes adopted by the Planning Collaborative include an upgrade of the facilities between the Harris Nuclear Plant and a substation at Research Triangle Park (RTP) from 115 kilovolts (kV) to 230 kV.
Therefore, Duke Energy Progress plans to invest an estimated $37 million in building a series of 230-kV transmission lines (approximately 22 miles total), and making other system upgrades, between a substation south of Apex and another in Research Triangle Park. A portion of the existing transmission system between Apex and Green Level will be upgraded to accommodate higher-voltage power lines. And easements acquired initially to accommodate a 115-kV transmission line will be used for the 230-kV line.
The project includes four major segments:
- The southernmost portion of the line, between the Harris Plant switching station (next to the plant) and the Apex U.S. 1 substation, spans about four miles and will be built almost entirely on Duke Enery Progress property. It is scheduled to be in service in mid-2014.
- The length from the Apex U.S. 1 substation to a substation in Green Level was built at 115 kV and put into operation in 2003. As the area's strong growth continues, the state Transmission Planning Collaborative confirmed that the completed 115-kV portion must be upgraded to 230 kV to increase system reliability. This will necessitate taking down the existing line (approximately 7.5 miles) beginning in late 2012 and building a new line on the same right of way. The new 230-kV line will require taller poles (approximately 100 to 110 feet above ground versus 80-foot height currently) set into concrete foundations. This portion must be completed by mid-2013.
- An approximately four-mile stretch between the Amberly 230-to-23-kV substation and a substation at Research Triangle Park was required and placed in service in mid-2009, including the new Amberly substation and new RTP 230-kV switching station at Research Triangle Park. The vast majority of this line segment parallels Highway 540.
- Approximately seven miles between the Green Level substation and the Amberly substation. The Green Level-to-Amberly portion of the line is planned for an already reserved transmission corridor. Duke Energy Progress cleared the right of way in 2010 and began line construction activities in September 2011. On this portion and the Amberly-to-RTP portion, initial easements were negotiated at 115 kV. But the easement agreement stipulates that the facility size can be changed. And planning information, confirmed by the Transmission Planning Collaborative, confirms this line now needs to be built at 230 kV. The Green Level 115-to-23-kV distribution substation also will be upgraded to a 230-to-23-kV distribution substation. This line segment, and the Green Level substation upgrade must be completed by December 2012.
- Two decades ago, this part of western Wake County was primarily farm and forest land. Since that time, however, the region has grown at a significant rate - with substantial additional development planned - and the electric system must keep pace. In addition to building new power plants, Duke Energy Progress must continually enhance the transmission and distribution systems to help ensure a continuous, reliable flow of electricity to homes and businesses in the region, and to provide adequate import and export capability for wholesale power through the company’s service area, as required by law.
- The need for the investment and upgrade to 230 kV was confirmed in a report by the N.C. Transmission Planning Collaborative. Without the transmission system upgrades, this rapid-growth area would exceed electric system capability in the near future, potentially creating the types of electric system reliability concerns that have plagued other parts of the country in recent years.
- Electricity is far too important for our customers to risk service interruptions or problems with power quality due to inadequate facilities. Duke Energy Progress has an obligation to ensure that the electric system is maintained and upgraded appropriately.
- High-tech companies and today's highly electronic homes and businesses need reliable, high-quality electricity. This project is intended to ensure the continuation of a reliable, high-quality flow of electricity in the future.
- The upgrades will enhance system reliability for electricity consumers throughout the region, not just Duke Energy Progress customers.
The transmission upgrades, when complete, are expected to generate more than $109,000 per year in Wake County in additional annual property tax revenues.
Maintaining a robust system for supplying and delivering electricity is integral in ensuring the continued economic prosperity of the region.
The additional transmission system investment will improve power quality and reliability in the area.
The project is expected to be built in phases, with construction occurring concurrently in several areas: A four-mile stretch between the Amberly substation and a substation at Research Triangle Park was placed in service in 2009. The remaining portions are expected to be built by mid-2014. A 7.5-mile portion of the route was built several years ago at 115 kV , so property easements are already established. That portion will be taken down and rebuilt at 230 kV (using the same easement). The portions between the Green Level substation and the Amberly substation, and from Amberly to the RTP substation, will be built on a corridor already identified but not yet in use. Duke Energy Progress has been acquiring easements from property owners along those routes.
The project requires a number of local, state and federal permits and approvals, as well as environmental and construction permits. Duke Energy Progress works with local governments and agencies to ensure that the project complements local growth plans. Duke Energy Progress complies with all regulatory requirements related to the construction and operation of the facilities. Before the development of any preliminary routes, Duke Energy Progress contacts the Corps of Engineers, the Fish & Wildlife Service, State Historic Presentation officer, the N.C. Department of Environment & Natural Resources and other agencies that have an interest in the project.
Duke Energy Progress believes public participation is critical to the success of any project. Among other communication initiatives, the company held public information meetings in the area to be served by the transmission facilities. The purpose of these meetings was to provide information on the need, scope and schedule of the project, and to answer questions the participants may have. Duke Energy Progress also made information available online and will continue to communicate directly with impacted property owners and others.
The line will require 35 feet, or slightly more, of right of way on both sides (70-foot total easement requirement). Duke Energy Progress pays fair value for easements, and landowners retain ownership of the property. Duke Energy Progress negotiates the right to cut trees off the right of way that could jeopardize the safe operation of the line. Duke Energy Progress does not expect to need to expand the easements already purchased to accommodate a larger transmission line.
Overhead vs. Underground
Duke Energy Progress investigated the possibility of putting portions of the line underground. Underground transmission lines have pros and cons. The reliability of underground transmission lines remains a question across the United States, as relatively few have been constructed. A fault in a buried line, caused by a manufacturing defect or an accidental dig-in, would take much longer to locate and repair than a similar fault in an overhead line. Other adverse factors regarding underground transmission lines are the effects they can have on wetlands and soil erosion and the decreased electrical capacity they can carry. They also tend to be significantly more expensive than overhead lines, and despite the common misperception that underground lines are out of sight, out of mind, their installation is often more environmentally intrusive than overhead construction.