Virginia State Corporation Commission (SCC) staff, in a March 13 report, concluded that Virginia Electric and Power d/b/a Dominion Energy Virginia has reasonably demonstrated that rebuilding the 500-kV Dooms-Valley Line #549 is necessary to continue providing reliable electrical service in the western Virginia region and beyond.
As noted by staff, Dominion Energy Virginia last September filed an application with the SCC requesting approval and a certificate of public convenience and necessity (CPCN) to build and operate electric transmission facilities in Augusta County, Va.
The company proposes to rebuild, entirely within existing right of way (ROW) that has been in use since about 1966, its 500-kV Line #549 from the existing Dooms substation to the existing Valley substation, located within August County. As part of the project, staff added, the company also proposes to use double-circuit structures providing capacity for the 500-kV line and an additional, underbuilt 230-kV line to be installed at a later date.
The company proposes to replace the 83 existing “COR-TEN” single-circuit lattice structures with 73 galvanized steel double-circuit lattice structures and 11 galvanized steel 3-pole angle structures, for a total of 84 replacement structures. Staff added that the company proposes to use a 500/230-kV double-circuit structure design (“5-2 Structures”), in which a 230-kV transmission line may be installed on the same structures as the 500-kV line. Dominion Energy Virginia states that it would file an application for a new 230-kV Dooms-Valley line at a future time should it become necessary.
Staff added that according to the company, assuming that a CPCN is granted by September, the projected in-service date for the project is June 1, 2020. Dominion Energy Virginia estimates a cost of $62m for the project, consisting of $58.7m for transmission line construction work, $2m for work at the Dooms substation, and $1.3m for work at the Valley substation.
According to the company, staff added, the project is needed to replace aging infrastructure that has reached the end of its service life, and to comply with mandatory NERC reliability standards. Staff noted that Dominion Energy Virginia asserts that the line is a critical component of the electric transmission grid, is an important part of the company’s 500-kV transmission network, and provides bulk power from generation sources, such as the Bath County pumped storage facility located to the west of the Valley substation, to major load centers.
The structures supporting the existing line were built of “COR-TEN” weathering steel between 1964 and 1966 as part of the company’s 500-kV “original loop, staff said, noting that it has verified the presence of “pack-out,” as well as evidence of concrete repairs on the existing line. Pack-out refers to the thickening layer of rust within bolted joints pushing the structural members apart, simultaneously stressing the joint and increasing the gap, allowing the cycle to perpetuate.
Staff also said that PJM Interconnection verified the NERC criteria violations and approved the project as a baseline upgrade (Project No. B2758). Specifically, the company identified thermal violations at the Lexington substation under two different failed breaker scenarios with the line out of service. Staff added that its power flow analysis confirmed that those violations do occur, and only when the line is not in service. Therefore, staff said, staff’s analysis supports the need for the 500-kV component of the project for compliance with mandatory reliability criteria.
Staff noted that it has some concerns regarding the company’s proposal to install 5-2 Structures to support a future, unidentified 230-kV line as part of the project. While the company references the general presence of a number of interconnection requests in the PJM Generation Queue for the project area, the company does not identify any specific anticipated need that would support building the 230-kV underbuild within 10 years of completion of the project. Also, staff added, Dominion Energy Virginia does not identify a specific need for the 230-kV circuit over the anticipated 60-year service life of the rebuilt line. If the need for a 230-kV line between the Dooms and Valley substations does not arise within the life of the rebuilt line, the additional impact of the incremental cost – about $6.1m – and excess height – about 16-18 feet – of the proposed structures would accrue without any benefit, staff said.
Staff noted that it believes that the choice between the proposed 5-2 Structures and a single-circuit option is a tradeoff between the certainty of the increased cost and height associated with the company’s proposal, which may prove to be unnecessary, versus the possibility that the single-circuit option may be inadequate to meet a need that, while not specified at this time, may arise at some unspecified point in the future.
Noting, for instance, that there has been little public opposition to the company’s proposed structures, staff said that it is not taking a position relative to the use of 5-2 Structures. However, staff said that it feels strongly that the case should not establish a precedent for any future similar proceeding in which the company is not able to provide a verified need for incremental facilities. Instead, each situation should be examined on a case-by-case basis, staff said.
Among other things, staff said that it continues to believe that chemical dulling of galvanized steel structures can be a reasonable and cost-effective means of visual impact mitigation.
Staff said that it agrees that the proposed routing in existing ROW reasonably minimizes impact to environmental, historic, and scenic resources. Accordingly, staff said, staff does not oppose the company’s request for a CPCN for the 500-kV line.