Entergy’s (NYSE:ETR) Entergy Mississippi on May 14 filed with the Mississippi Public Service Commission a petition for a certificate of public convenience and necessity (CPCN) seeking authorization to acquire, build, expand, own, operate, and maintain a new 230-kV substation between Flora, Miss., and Canton, Miss.
The company added that the proposed electrical facilities include:
- The substation, which would be built as a six breaker ring bus substation – initially operated as five breaker ring – and eight feeder bays on property to be acquired within the Madison County Mega-Site
- 230-kV terminal facilities at the existing South Canton substation that would be expanded to facilitate a new 230-kV line and related facilities. A 230-kV line bay would be added to the existing South Canton substation
- Line panels and relays that would be upgraded at the existing Tinnin Road and Yandell Road substations
- One power transformer and four feeder bays that would be installed at the proposed Catlett Road substation, but may not initially have end-use customers taking service
- Three new transmission lines – about 8.4 miles in length in total – that would be built from the proposed Catlett Road substation to the existing South Canton 230-kV substation for 3.6 miles; and from the proposed Catlett Road substation to a tap point on the existing Tinnin Road Substation to Yandell Road Substation transmission line utilizing two 2.4-mile parallel lines
- 5.8 miles of new 12.47-kV distribution lines that would be built to support area distribution needs and to enhance distribution reliability
The estimated $57.7m project is within Madison County, Miss., the company said. The costs of the proposed electrical facilities would be reflected in the company’s rates through the operation of Entergy Mississippi’s formula rate plan and through commission order, the company said, adding that it currently estimates that the revenue requirement associated with the proposed electrical facilities would result in an approximately 61-cent impact on a typical residential customer’s monthly bill.
The primary purpose of the proposed electrical facilities is to enhance the electrical supply and service reliability for residential, commercial, and industrial loads – and the projected new load growth in the Madison and Canton areas; as well as to reduce the likelihood of customer interruptions in the area during planned or unplanned overlapping outage events.
Entergy Mississippi added that the proposed electrical facilities would provide greater operational flexibility and increased reliability for the transmission and distribution facilities in the area. Increased distribution reliability would be achieved by adding a new substation point of delivery to the area, which would reduce the amount of load served from the existing South Canton and Yandell substations, the company said.
The proposed electrical facilities would also mitigate the risks of low voltage constraints that could result on the 115-kV and 230-kV transmission networks in central Mississippi during an overlapping outage scenario where a planned or forced outage on a 230-kV line is followed by a second unplanned outage of an additional 230-kV line, the company said. That kind of outage scenario is classified as a category P6 event in the NERC TPL-001-4 reliability standards and would result in the inability to serve upwards of 50 MW to 100 MW of area customers load, which represents a risk in the inability to serve up to about 17,000 customers until the failed equipment or elements are restored back to service, the company said.
The potential low voltage is projected across a wide geographic area ranging from Canton to just south of Greenwood, Miss., as well as areas to the west, including Yazoo City, Miss., the company said.
Hinds County project
On May 15, Entergy Mississippi filed with the commission a petition for a CPCN seeking authorization to acquire, build, expand, own, operate, and maintain a new 115-kV substation near the University of Mississippi Medical Center (UMMC) Campus in Jackson, Miss., and connect the new substation to the transmission line from the existing Rex Brown substation to the Monument Street substation, as well as to the 115-kV transmission line to the existing Fondren substation, about a half-mile to the east.
The company added that the proposed electrical facilities include:
- The new substation, with a five-breaker ring bus configuration to accommodate three line terminals – with an ultimate arrangement of four line terminals and six transmission breakers – that would be built on property located on the southwest corner of North Mill Street and Lorenz Boulevard in the area of Jackson
- The proposed substation would have two new 115-kV/13.8-kV, 40 MVA transformers connected to a 13.8-kV bus that includes eight feeder breakers, two main breakers, and one bus tie breaker
- A new 115-kV line terminal that would be built at the Rex Brown substation with a rebuilt 115-kV double-circuited transmission line from Rex Brown to the corner of Forest Avenue and Watkins Drive on existing right of way (ROW). From that point, about 2.9 miles of the existing transmission line on Watkins Drive would be rebuilt from the Hico substation to the proposed substation
- About 0.63 miles of transmission line that would be altered from the corner of Mill Street and Mitchell Avenue to the existing Fondren substation and integrated with distribution facilities
- The existing overhead static wire from the Monument Street substation to the proposed substation 115-kV transmission line that would be replaced with 48 fiber optical ground wire
The project is located in Hinds County, Miss., the company said, noting that the proposed electrical facilities are needed to maintain compliance with mandatory NERC reliability standards by mitigating the potential for a cascading service interruption. Analyses have indicated that the simultaneous loss of the Rex Brown-Monument Street 115-kV transmission line and the South Jackson 230/115-kV autotransformer could result in an outage event across the central Entergy Mississippi footprint, including most of the metro area of Jackson.
The company added that the proposed electrical facilities are also needed to enhance the electrical supply and service reliability for existing commercial and residential customers in the Fondren area of Jackson, as well as to meet the projected load growth in the area.
The total estimated cost of the proposed electrical facilities is $43.9m, Entergy Mississippi said, adding that subject to the receipt of necessary permits and required approvals, the project is currently planned with an in-service date of December 2020.
The company said that the costs of the proposed electrical facilities would be reflected in its rates through the operation of Entergy Mississippi’s formula rate plan and through commission order. Entergy Mississippi added that it currently estimates that the revenue requirement associated with the proposed facilities would result in an approximately 49-cent impact on a typical residential customer’s monthly bill.