Delmarva Power is seeking approval from the Maryland Public Service Commission (PSC) to rebuild part of a 138-kV transmission line in efforts to resolve an anticipated reliability violation (Case No. 9321).
Delmarva Power filed on April 12 an application for a certificate of public convenience and necessity (CPCN) to rebuild the Maryland portion of a 5.25-mile, 138-kV transmission line beginning at the company’s Glasgow substation in New Castle County, Del., to its Cecil substation in Cecil County, Md., all within existing right-of-way (ROW).
The company referred to the portion of the line from the Maryland/Delaware state line to the Cecil substation as the “entire Maryland project.”
More specifically, Delmarva Power said, the application seeks the issuance of a CPCN to rebuild 2.05 miles of high-voltage alternating current (AC) transmission circuit from the Maryland/Delaware state line to the Amtrak railroad corridor in Cecil County – referred to as “Section 1” of the entire Maryland project.
The upgraded 5.25-mile, 138-kV transmission line from the Glasgow substation to the Cecil substation will resolve an anticipated thermal N-1-1 reliability criteria violation that could, if left unaddressed, disrupt the transfer of power from generation sources in Cecil and Harford counties in Maryland, and sources north and west into the Delmarva Peninsula as early as June 2015.
Delmarva Power also said that under PJM Interconnection’s regional transmission expansion plan (RTEP), this rebuilt 138-kV transmission line must be in operation by June 1, 2015. Consequently, construction must begin in Maryland by September 2014 and end by May 2015.
While Section 1 of the entire Maryland project will be energized at 138 kV of alternating current, it will be designed and built so that it may be energized at 230 kV at a future time with modifications at the Glasgow and Cecil substations as well as to Section 2 of the project.
Delmarva Power also said that the total estimated annual operating cost of Section 1 of the entire Maryland project is $147,280, with financing coming from internal and external sources.
Based on the estimated $5.7m overall cost of the entire Maryland project, the initial annual charge or annual revenue requirement attributable to the entire project will be about $1.2m, which translates to a $288 per MW-year charge, effective on June 1, 2015.
The entire Maryland project is driven by in-service date requirements and constraints on coordination of many other system outages required over the next few years.
Delmarva Power added that construction of the entire Maryland project must be done in a way that does not reduce the electric system’s reliability below acceptable limits and that respects time-of-year restrictions that may be associated with any necessary environmental permits.
The reliability concern is based on the fact that existing transmission facilities in the entire Maryland project ROW must be taken out of service in order to rebuild the transmission line and terminate the rebuilt line into the appropriate bus positions at the Glasgow and Cecil substations.
Delmarva Power added that the PJM 2010 RTEP identified an anticipated violation of PJM N-1-1 criteria under which an unacceptable thermal overload result was shown for the contingency pairing consisting of the 230-kV transmission line between the Bradford substation in Chester County, Pa., the Clay substation in Chester County and the Colora substation in Cecil County; and the 230-kV transmission line between the Conowingo substation in Harford and Cecil counties and the Colora substation.
This particular outage combination would cut off two 230-kV transmission lines originating from generating sources in Cecil and Harford counties and points north and west of the Delmarva Peninsula, Delmarva Power said.
Upon realizing that contingency pairing, a significant amount of load would be served from a long radial 138-kV transmission line originating from the Glasgow substation.
The company also said that if the entire Maryland project is not timely built, it would be in violation of the reliability criteria tests identified by PJM. If the identified contingencies were to occur, the consequences could lead to customer interruptions, most likely in Cecil and Harford counties. Furthermore, in the most extreme case, Delmarva Power added, the unacceptable thermal conditions could lead to failure of transmission facilities, which could result in extended repairs and customers being without power for longer durations.
Delmarva Power is a subsidiary of Pepco Holdings (NYSE:POM).