A technical hearing will be held on March 22 at the Vermont Public Service Board (PSB) Hearing Room in Montpelier, Vt., regarding the joint petition of Vermont Transco LLC and Vermont Electric Power Company, collectively VELCO, for a certificate of public good authorizing the construction of the Connecticut River Valley Project.
As noted on the PSB website, the project consists of transmission line and substation improvements in the Towns of Cavendish, Chelsea, Hartford and Weathersfield in Vermont. According to the September 2015 petition, the project is intended to improve local and regional system reliability in the Connecticut River Valley and includes additions and modifications to VELCO’s existing 115-kV substations at Ascutney, Chelsea and Hartford, and to the 115-kV transmission line from the Coolidge substation to the Ascutney substation (K31 Line). The proposed project has four components, the petition added:
- Reconductoring and rebuilding the K31 Line
- Adding a +50/-25MVAr Static VAR Compensator (SVC) reactive device adjacent to the Ascutney substation and adding a new bay at that substation to accommodate the reactive device
- Rebuilding the Chelsea 115-kV substation into a three-breaker ring configuration
- Dividing the 25MVAr capacitor bank at the Hartford substation into two 12.5MVAr capacitor banks
The project’s total estimated cost is about $122.5m, including about $51.6m for the Coolidge to Ascutney (K31) Line Rebuild, about $36.7m for the Ascutney SVC addition, and about $20m for the Chelsea substation expansion.
Assuming PSB approval by Sept. 1, the schedule for project construction extends from 3Q16 through 2Q18, the petition added.
Related to the project, at a later date, Green Mountain Power (GMP) intends to reconductor four 46-kV line sections totaling about 20 miles: the East Middlebury to Smead Road Line, the Smead Road to Silver Lake Line, the Taftsville to Bethel Line, and the Windsor to Taftsville Line. Those upgrades, the petition added, were considered together with the project in connection with the alternatives analysis reviewed in the ISO New England and the Vermont System Planning Committee processes. GMP will separately seek the PSB’s approval to do that work, the petition said.
The project is required to meet the need for present and future demand for service, which could not otherwise be provided in a more cost-effective manner through energy conservation programs and measures, as well as energy efficiency and load management measures.
The petition also noted that the project is needed to address reliability concerns in the Connecticut River Valley that were identified during an N-1-1 contingency analysis, which is applicable under NERC reliability standards. The analysis identified various reliability concerns including a potential overload on the Coolidge to Ascutney K31 line, high voltages and low voltages near the Hartford 115-kV substation, as well as voltage collapse in the Connecticut River Valley, according to the petition.
Of the K31 Line, the petition noted that VELCO proposes to reconductor about 14 miles of that line, which consists of replacing the existing conductor with non-specular 1351 ACSS conductor. That improvement would allow the line to be operated at a higher temperature, which increases the capacity of the line with little change to the line’s physical appearance. Additionally, VELCO would replace the most of the existing structures with new structures having essentially the same appearance and with limited exceptions, marginal increases in height – eight-foot average – to improve the safety and reliability of the line. There are two structures that would have significant increases in height in order to eliminate the replacement of two existing structures located within a significant environmental resource.
Of the Ascutney substation, the petition added that that component involves installing a +50/-25 MVAr SVC, with Thyristor Controlled Reactors and Filter Capacitors, adjacent to that substation. A new bay, with three new 115-kV breakers, would be added at that substation to connect the new SVC. The petition added that this improvement will correct high/low voltage issues and provide voltage support to the system to avoid regional voltage collapse in the event of identified system outage scenarios.
Discussing the Chelsea substation, the petition noted that the 115-kV portion of that substation would be rebuilt into a three-breaker ring configuration, adding that to accommodate that improvement, VELCO would build a new control building and expand the fence line. That improvement would allow Chelsea area load to remain in service when either of the two sources – the Hartford and Granite substations – that connect to the Chelsea substation are out of service in the event of a line or line-associated bus contingency.
Additionally, while the project is being built, VELCO would take advantage of the opportunity to perform regular condition-based maintenance at the Chelsea substation, including the replacement of some of the older components, and protection and control equipment with new components and equipment.
Of VELCO’s Hartford substation, the petition added that the existing 25 MVAr capacitor bank at the substation would be reconfigured into two 12.5 MVAr capacitor banks, allowing more operational flexibility as well as optimal use of capacitors and the proposed Ascutney SVC. While the project is being built, VELCO would also perform regular condition-based maintenance at the Hartford substation.
The petition also noted that the project would not unduly interfere with the orderly development of the region, and is consistent with the Cavendish, Chelsea, Hartford and Weathersfield town plans, as well as the plans of Southern Windsor County and the Two-Rivers Ottauquechee Regional Planning Commissions.
Among other things, the petition noted that the project would have no undue, adverse effects on stream resources, and VELCO has avoided locating pole replacement in regulated streams, thus not affecting the physical attributes of stream watercourses, streambed substrate, banks or fish habitat.
Also, the petition said that the project would not have an undue adverse impact on aesthetics or natural beauty, and the project upgrades will result in a limited increase in visibility of the electrical transmission infrastructure from surrounding public vantage points.
Furthermore, the petition said that the project would not have an undue adverse effect on rare and irreplaceable natural areas, and it will not have an undue adverse effect on necessary wildlife habitat.