Potomac Electric Power Company (Pepco) is seeking approval from Maryland state regulators to rebuild an existing 9.9-mile, 230-kV double circuit tower line (DCTL) in Prince George’s County, Md., that the company said must be in operation by June 1, 2015.
The company filed on June 21 an application with the state Public Service Commission (PSC) for a certificate of public convenience and necessity (CPCN) to rebuild the line beginning at the company’s Burtonsville substation and running to its Takoma substation, all within existing right-of-way.
Project completion will reduce the risk of a potential post-contingency overload that could occur if the rebuild was delayed until the 2015/2016 winter period, Pepco said.
Additionally, replacing the infrastructure currently supporting the two high-voltage alternating current (AC) tower circuits that will be rebuilt promotes Pepco’s emphasis on replacing older assets with newer facilities, and will replace temporary infrastructure enhancements currently in place to ensure conformance with NERC clearance requirements.
The rebuilt line must be in operation by June 1, 2015, Pepco added, noting that it must begin construction by June 2014 and complete the entire project by May 2015.
The currently estimated capital cost to build the line is $35m, with the substation costs estimated to be $6m and the transmission costs estimated at $29m.
Financing for the project will come from a combination of internal and external sources, with the largest funding source coming from external sources and will include corporate debt or other similar securities of Pepco, as well as potential issuances of debt and/or equity at parent company, Pepco Holdings (NYSE:POM), the proceeds of which would be contributed to Pepco in order for it to maintain its targeted capital structure and investment grade credit ratings.
Pepco also said that the construction investment will become a part of Pepco’s FERC-regulated transmission rate base and the charge to recover those costs will be billed to all transmission service customers in the Pepco zone through PJM.
The existing Burtonsville to Takoma right-of-way currently has two 230-kV DCTLs. Pepco also noted that one set – the West Line – was rebuilt in 1992 and is supported by single steel pole structures. The set to be rebuilt – the East Line – is supported by lattice tower structures that have been in place since 1958.
The age and condition of the existing Burtonsville to Takoma East Line is deteriorating and could result in prolonged power outages if it fails.
The tower line will be changed from a horizontal phase configuration to a vertical phase configuration.
Pepco also noted that the existing lattice tower structures will be permanently removed from the right-of-way and will be replaced by the new double circuit single steel pole structures, which will be offset 62.5 feet from the right-of-way centerline.
The project was identified through the annual Pepco system planning process, which is a systematic set of activities inclusive of testing the transmission system using load flow analysis and forecasted load versus available capacity comparisons to ensure compliance with all PJM Interconnection and internal Pepco planning criteria.
The process considered the forecasted winter loads for the Takoma and Metzerott system in conjunction with several constraining factors, including the system configuration, winter load requirements, load growth, the anticipated outage window during the rebuild of the East Line and aging infrastructure.
Pepco also said that it determined that replacement of the East Line would require an eight-month outage, during which the West Line will supply the load in the Takoma and Metzerott system.
With the East Line out of service, the system must be able to withstand an N-1 event. That is, the West Line must be able to supply the Takoma and Metzerott systems in the event of a fault on one of the West Line circuits. Therefore, Pepco added, to ensure no loss of load during the rebuild of the East Line, the rebuild must be completed during a time of year when the forecasted highest load exceeding the emergency capacity of the West Line will not occur.
In a recent filing with the PSC involving summer reliability, Pepco noted that several projects have been planned over the next five years that will increase reliability, including: upgrading one 230-kV circuit and converting one 138-kV circuit to 230-kV with associated equipment from the Buzzard Point substation to the Ritchie substation; upgrading a 230-kV line the Dickerson substation to the Quince Orchard substation; upgrading two 230-kV lines from the Burtonsville substation to the Bowie substation; and upgrading the 230-kV tower-line from the Burtonsville substation to the Takoma substation.