Delmarva Power & Light on Aug. 24 filed with Virginia state regulators an application for a certificate of public convenience and necessity to build the Virginia portion of a new 30.9-mile, 138-kV transmission line from Delmarva Power’s Piney Grove substation in Wicomico County, Md., to its Wattsville substation in Accomack County, Va.
The company on Aug. 24 filed with Maryland state regulators for a CPCN to build the Maryland portion of the line.
In its application filed with the Virginia State Corporation Commission, the company said that as part of the project, it would rebuild the 69-kV transmission lines spanning from the Piney Grove substation to the company’s Kenney substation in Worcester County, Md., and from the Kenney substation to the Wattsville substation.
The total length of the project is 30.9 miles long, 6.15 miles of which will be built in Virginia in an existing right of way. The estimated cost of the entire proposed project is $44.7 million, and the estimated cost of the Virginia project is $8.9 million, the company added.
The new 138-kV line from the Piney Grove substation to the Wattsville substation must be in place by June 1, 2018, and has been properly included in PJM Interconnection’s regional transmission expansion plan (RTEP), the company said.
Discussing the need for the project, Delmarva Power said that PJM identified a post-contingency violation during the application of the baseline generation deliverability testing criteria while studying its planning cases for 2018: an unacceptable thermal overload on the 138-kV transmission line spanning from the company’s Piney Grove substation to its New Church substation in Accomack County that could, if left unaddressed, disrupt the power flow from generation in the Virginia section of the Delmarva Peninsula and adversely impact reliability as early as June 2018.
The unacceptable thermal overload on the Piney Grove—New Church Line is associated with multiple common mode contingencies, including the fault of a 138-kV circuit breaker at either the Kings Creek substation in Somerset County, Md., or at the Oak Hall substation in Accomack County, the company said.
The common mode outage of a circuit breaker at the Kings Creek substation results in the loss of the 138-kV transmission line from the Kings Creek substation to the Pocomoke substation in Worcester County, and the 138-kV transmission line from the Kings Creek substation to the Loretto substation.
The company also said that the common mode outage of a circuit breaker at the Oak Hall substation results in the loss of the 138-kV transmission line from the Pocomoke substation to the Oak Hall substation and the 138-kV transmission line from the Oak Hall substation to the New Church substation.
Delmarva Power said that it concluded, and PJM agreed, that the project is the best and most efficient long-term solution to resolve that reliability criteria violation.
In addition, the 69-kV transmission line that spans from the Kenney substation to the Wattsville substation and is partially located in Virginia was identified to be rebuilt in PJM’s 2011 RTEP.
That line, Delmarva Power added, along with the 69-kV transmission line that spans from the Piney Grove substation to the Kenney substation in Maryland, must be replaced to address the risk associated with its age and condition.
“The project is therefore a critical component of the electric transmission grid that serves Virginia and Maryland, and will help Delmarva Power maintain the overall long-term reliability of its transmission systems as its customers require more power in the future,” the company said.
Among other things, the company said that the existing 69-kV single overhead transmission lines in the ROW are currently on single wood pole structures that were originally installed in the 1940s and have reached the end of their useful lives.
The wood structures will be permanently retired and the 69-kV lines and the new 138-kV line will be installed on single steel pole structures, which will carry the circuits in a side by side vertical configuration. The company also said that most of the new single steel pole structures will range from 80 feet to 120 feet above ground in height, and a small number of structures will range from 60 feet to 135 feet above ground.
Using the existing ROW minimizes land fragmentation, avoids new resource impacts and avoids additional operational costs associated with obtaining and maintaining new ROWs, the company said.
Delmarva Power said it will avoid and minimize impacts to sensitive resources such as wetlands, wetland buffers and cultural resources areas within the existing ROW by engineering and planning the location of new poles in areas that avoid those resources.