Chronic System Congestion in Southwest Connecticut was Reduced Significantly about a year ago, while saving ratepayers US$150 million.
The Bethel-Norwalk (B-N) project is a significant component of a suite of 345-kV and 115-kV system upgrades in this area. To describe B-N as complex would be an extreme understatement. The B-N project entailed more than 11 miles (18 km) of new 345-kV underground transmission cable, two new 345-kV gas-insulated substations, three transition stations and more than 20 miles (32 km) of new overhead 345-kV line. Yet, Northeast Utilities (NU; Berlin, Connecticut, U.S.) energized this landmark project two months ahead of schedule and US$15 million under budget.
So, how does a utility energize a major 345-kV upgrade ahead of schedule and under budget in one of the most congested areas of the United States, while overcoming stiff public opposition, solving complex technical challenges, and navigating stringent regulatory and statutory requirements?
THE RIGHT PROJECT PLAN
Prior to the completion of the B-N project, southwestern Connecticut was of particular concern to regional transmission planners, mostly because of an inadequate 345-kV transmission backbone in the growing Stamford and Norwalk, Connecticut, communities. Without a new connecting 345-kV line, NU would not be able to guarantee uninterrupted service during peak use, the region would become even more dependent on expensive imported power and NU would likely continue to accrue stiff congestion charges from purchasing this power.
Even though the project had a compelling need, the challenges were creating and implementing a plan that would get approved and built. With the potential for entrenched public opposition, agency objections and technical design hurdles, the project could have easily been mired for years. Executing a sound project plan was critical to project success. NU's project execution plan consisted of:
Design-bid-build project approach
Cooperation and communication with affected communities
Proactive routing and designs that mitigated opposition
Team approach with consultants and contractors
Innovative construction processes
Carefully developed energization plan.
DESIGN-BID-BUILD MADE SENSE
When faced with a major capital project, utilities today are often tempted to use a design-build rather than the traditional design-bid-build approach because of the assumption that the design-build approach will free up their internal resources and cost less. However, when a capital project has several unknowns and many risk factors, especially involving routing and technical issues, design-build can end up being quite costly and subject to unexpected delays.
NU used a traditional design-bid-build approach on this complex project. Although it required a full-time project director and project team from NU's staff, this approach allowed greater control, maximized the capabilities of consultants and contractors to design and construct the line, and ultimately encouraged closer cooperation and greater efficiency on a complicated project. By being involved with the design and consultants in a team approach, NU's engineering and project managers gained valuable experience on the design, construction and operation of the project. That spirit of cooperation and teamwork were significant factors in the project's early completion and under-budget success.
The B-N project was more than five years in the making. In 2001, NU filed an application with the Connecticut Siting Council (CSC) for a new 345-kV line stretching from NU's Plumtree substation in Bethel to the Norwalk substation. NU hired POWER Engineers Inc. (POWER; Hailey, Idaho, U.S.) to assist with preliminary design concepts during the CSC review period.
NU's initial application included a preferred route and solution (a 115/345-kV overhead line in an existing right-of-way) as well as potential alternatives. The CSC requested a total of 21 variations using overhead and underground combinations, which would effectively hide the transmission lines from view. The CSC finally approved a hybrid variation using two different underground cable technologies at two different voltage levels and gas-insulated substation additions. The route “porpoised” from overhead to underground at several points, traversing developed areas, historic districts and schools in four towns. It also passed through semi-rural existing right-of-way corridors. NU's ultimate goal in designing the new line was to identify a solution that was technically feasible and still acceptable to all involved.
One of the keys to success was engaging the public and keeping them informed throughout the life of the project. From the outset, NU forged effective relationships with organizations that could potentially oppose construction. NU also kept property owners, municipal officials and state regulatory agencies apprised of project progress. NU disseminated information through kiosks in town halls, maps and traffic updates on websites, newspaper articles and advertising to keep the public and stakeholders informed and engaged throughout the entire project (see Transmission & Distribution World, “Open House Communications,” April 2006).
COMMUNITY CONCERNS ADDRESSED
With the major project roadblocks out of the way, NU proceeded with detailed design, keeping POWER on board as the primary design consultant. Designs and associated studies for the following facilities were executed during this phase of the project:
8.7 miles (14 km) of overhead transmission line (varying structure types, including wood laminate H-frame, steel monopole 345/115 kV and steel monopole 345 kV).
More than 11 miles of 345-kV underground transmission line, including: 2.1 miles (3.4 km) of cross-linked polyethylene (XLPE) cable between the Plumtree substation and the Hoyts Hill transition station; a 9.7-mile (15.6-km) high-pressure fluid-filled (HPFF) cable line between the Archers Lane and Norwalk Junction transition stations; and 9 miles (14 km) of 115-kV XLPE underground lines to clear rights-of-way for the 345-kV overhead lines.
Three new transition stations (Hoyts Hill, Archers Lane and Norwalk Junction) for changing the overhead 345-kV line to underground, additions to the existing Plumtree substation for reactors and the 345-kV underground terminations, and overhead and underground terminations at the existing Norwalk substation.
The designs had to balance system needs and community concerns. To describe the visual impacts of these facilities for public review, POWER prepared renderings and photo simulations. Each of the transition stations required special designs and significant public involvement to gain approval.
For example, the Hoyts Hill transition station for the 345-kV XLPE was on a scenic designated roadway, which made visual impacts a major concern. To mitigate these issues and to obtain the town of Bethel's approval, the station was cut into a hillside and designed with low-profile structures and landscaping, including retaining walls with a decorative facade to blend with the background. At another location, a section of the 115-kV overhead line located on school property was replaced with underground solid-dielectric cables, thereby gaining the support of the Bethel town executives and residents.
A TEAM APPROACH
To limit financial risk, maximize control and provide valuable training to staff, NU set up one-for-one counterparts for tasks that required special expertise or large teams. For example, when POWER had an underground-line engineering manager working on the underground portions of the project, NU had its own underground engineer assigned to that part of the scope.
This approach gave NU employees hands-on training on several technical innovations. This project was NU's first installations of 345-kV transmission cable on its system. And, the 345-kV XLPE circuit between the Plumtree substation and the Hoyts Hill transition station was one of the first U.S. installation of 345-kV solid-dielectric cables installed in a duct bank with splices. It was also the longest length installed to date.
In addition to the major contractors listed in the table, NU also hired specialty contractors for traffic management and environmental monitors. Because of project familiarity gained during the engineering and design phase, POWER was retained to act as the construction manager for the project. To facilitate construction, which began in spring 2005 and ended in July 2006, POWER set up a project site office in Bethel and hired a local team of contract administrators, construction managers, inspectors and office staff.
One of the major concerns of the public was the impact of construction. Thanks to the proactive efforts the B-N team took early on, these concerns were anticipated and mitigated.
For example, the line passed through several schools, raising safety concerns. The B-N team took exceptional measures to ensure the safety of schoolchildren around the construction sites. In one case, the contractor hired a chaperone to escort each student to and from a special bus the contractor had rented to move safely around big equipment and trenches during construction. This kind of commitment allowed the construction for the B-N project to proceed even while school was in session, avoiding significant schedule impacts.
The underground construction was particularly challenging. A significant portion of the underground segment was on busy U.S. Route 7. The highway carries most of the commuter traffic from south central Connecticut to the work centers farther south toward New York. Because of this heavy daily traffic, NU took traffic control to a new level and scheduled most of the major underground work at night. The work on state highways had to be closely coordinated with the Connecticut Department of Transportation, which was also in the midst of widening the highway in the same location the B-N underground lines were scheduled to be installed.
As construction manager, POWER was NU's on-site representative, charged with managing the construction effort to meet budget, schedule, safety and environmental goals. Because of the site constraints, work had to be sequenced with tight time frames to minimize costly construction down times. These constraints sometimes resulted in creative scheduling efforts.
The Archers Lane transition station site was accessed 0.25 miles (0.4 km) from the main road by a 20-ft (6-m)-wide road. This was not wide enough to give access to the site while the cable pipes were being installed. POWER coordinated and scheduled the construction of the transition station, the underground cable installation and termination, and the overhead line stringing so that each contractor could have access to finish their portion of the work while also meeting the construction schedule.
At the Norwalk Junction transition site, ground grid installation, HPFF vaults and cable pipe installation, overhead line stringing into the transition site, and reactor delivery and assembly were all occurring at the same time. To meet the schedule, the vaults were installed on a weekend; the underground cables were installed on the south end of the yard, while shunt reactor assembly occurred on the north end. As soon as the north reactor was completed, the crews traded places with the underground contractor. While this was going on, grounding installation was allowed to proceed as long as it did not impact the underground work or shunt reactor assembly. As soon as grounding installations were completed in the middle of the site, the overhead line contractor was allowed to string the overhead line into the station.
CAREFULLY DEVELOPED ENERGIZATION PLAN
Energization required thorough planning that would minimize cable failure risk. Previously, there had been 345-kV cable energization failures in other parts of the United States. NU reviewed and considered these issues while developing a plan to energize B-N to ensure successful energization. Although details of the other failures were limited, NU obtained as much information as possible — even conducting extra studies (including transient recovery voltage, switching and others) to develop an energization sequence that would minimize cable risk.
The line was energized in segments. A lengthy and complex process was used that involved energizing each 345-kV circuit segment for 24 hours followed by de-energization. B-N's successful energization resulted from the planned, stepped sequences developed by NU and a commitment not to rush the process.
PAVING THE WAY FOR THE FUTURE
The project success was due in large part to the execution of the project plan. NU took steps early and often to identify potential challenges (whether they be public opposition or technical complexity) and used a traditional design-bid-build approach that gave NU the control it needed to anticipate and address the challenges. By balancing the needs of local communities with the energy requirements of the larger state, NU built a reliable transmission project ahead of schedule and under budget.
But B-N is not just a past success, its success has important ramifications for NU's future transmission build-out. The B-N success has lent credibility to NU's other New England transmission projects and positioned the company as one of the foremost authorities on new transmission construction. Throughout the B-N project, NU developed processes that have proved useful for its future projects: a process for institutionalizing lessons learned, a process for fast and flexible field changes, a process for getting involvement from impacted state agencies, and a process for monitoring the schedule and budget.
With this development of strong project management and the demonstrated ability to execute large projects, NU proves that major transmission projects aren't just things of the past; they're alive and well today.
Laurie Aylsworth is Northeast Utilities' vice president of Transmission Projects, Engineering and Maintenance and had been the project director for the Bethel-Norwalk project. After B-N, she led NU's New England East-West Solution, a project of more than 180 miles of transmission line across three New England states. Aylsworth has been with NU since 2004. She is a graduate of Colorado State University, where she earned a bachelor of science degree, and of Chicago's Graduate School of Business Executive Program in Corporate Strategy.
Rich Mues is a senior project manager for POWER Engineers in St. Louis, Missouri. Mues earned a BSEE degree (power option) from the University of Missouri at Rolla. He is a registered professional engineer in 11 states, including Connecticut. A member of IEEE, Mues has been a consulting engineer for more than 30 years. After B-N, Mues has been engineering project manager on other New England projects, including the Killingly, Beseck and East Devon 345-kV substations for Northeast Utilities.
|POWER Engineers||Engineering and construction management|
|Coler and Colantonio||Right-of-way acquisition subcontractor to POWER|
|URS||Surveying subcontractor to POWER|
|Mitsubishi Electric Ltd.||Supplied GIS equipment at two substations|
|McPhee Electric Ltd., LLC||Substation civil and electrical, transition stations construction|
|Siemens||Furnished and installed three shunt reactors|
|W.A. Chester||Furnished and installed 10 miles of 345-kV HPFF underground cable|
|Kiewit Construction||Furnished and installed 10 miles of 115-kV XLPE underground cable|
|New River Electrical Corp.||Constructed 345-kV XLPE underground cable system|
|Silec||Furnished 345-kV XLPE underground cable and accessories|
|M.J. Electric||Constructed 345-kV overhead line|
|Blakeslee Arpaia Chapman||Transition stations civil contractor and 345-kV XLPE civil subcontractor to New River|
|Sertex||Furnished and installed fiber-optic cable system|
|Clarence Welti||Geotechnical services subcontractor to POWER|
|Geotherm||Geotechnical services subcontractor to POWER|