Arkansas Electric Cooperative Corporation (AECC) on Dec. 17 filed with the Arkansas Public Service Commission an application for a certificate of environmental compatibility and public need (CECPN) to build, own, and operate a new 161-kV switching station; an 18-mile, 161-kV transmission line; and the 161-69-kV Partain substation in Van Buren County, Ark.
AECC said that it requests a commission order by June 17, 2019, adding that if such approval is granted, the project would have an anticipated in-service date of Dec. 1, 2020.
The project is the first phase of a two-phase plan to build a 161-kV transmission loop between Clinton West and AECC’s Heber Springs North 161-69-kV substation to reinforce the 69-kV networks of Petit Jean Electric Cooperative Corporation (PJECC) and First Electric Cooperative Corporation (FECC).
AECC added that the switching station would connect to an existing Entergy (NYSE:ETR) 161-kV line that runs between Entergy substations at Quitman in Faulkner County and Hill Top, near Gilbert in Searcy County, and would provide a 161-kV source for the new transmission line.
The switching station and the new line would together supply the Partain substation, which would result in a new transmission source to PJECC and FECC.
The switching station would be built using four 161-kV circuit breakers, foundations, support steel, electrical bus work, a control building, and associated high voltage metering and switching equipment. AECC added that a 161-kV breaker would be installed for each of the four elements connected to the switching station, and would be designed for a “ring bus” to allow increased reliability as required for such connections.
The line would be built using steel pole structures, typically spaced about 500 feet to 800 feet apart. An “H-frame” design would be used due to its strength and the long spans required to traverse the hilly terrain along the proposed route. AECC also said that structures at angles would require guying, and to improve aesthetics, the line would be built using weathering steel poles.
The preferred route for the new line is alongside the right of way (ROW) of an existing 69-kV, wooden H-frame – two-pole – transmission line owned by PJECC. AECC added that the existing ROW width of 100 feet would be widened by 60 feet to accommodate the new line. The new ROW would overlap – share – part of the ROW of the existing line to minimize the total new ROW required by 40%, AECC said.
The Partain substation would be a 161-69-kV substation that would have a 100 MVA transformer, a 161-kV breaker for transformer protection, two 69-kV line breakers for two outgoing 69-kV circuits, foundations, support steel, electrical bus work, a control building, as well as associated high voltage metering and switching equipment.
Discussing the need for the project, AECC said that loads have outgrown the existing 69-kV line, and that load in the area is served using only two single sourced, radially operated lines. As such, any fault along the 69-kV line has the ability to leave all downstream substations without service from the location of the fault to the Edgemont open point. As a result, AECC added, retail consumers are subject to a service disruption until the fault can be cleared or until the member cooperative can reconfigure its distribution system to temporarily serve the affected loads.
Providing a 161-kV transmission loop – phase 1 and phase 2 of the total project – would provide three 69-kV transmission sources – Clinton West, Heber Springs North, and the substation – to the existing 69-kV line. AECC added that once both phases are complete, power and energy could be transmitted both east and/or west along the existing 69-kV line, which would allow outages on the 69-kV line to be isolated and sectionalized, thus leaving the remaining substations and their associated retail consumers unaffected or with greatly reduced outage times.
Such enhanced service would also reduce the expense and increased hazard of working the existing 69-kV line while it is energized, AECC said.
Among other things, AECC said that the estimated cost of the project is $28m – that is, $4m for the switching station, $20m for the transmission line, and $4m for the Partain substation.