ID 3206886 © Vladimir Konjushenko |
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Entergy Mississippi Seeks Regulatory Approval To Upgrade 500-kV Substation In Mississippi

June 2, 2021
The company said that the total cost of the proposed facilities is estimated to be $13.8m.

Entergy’s Entergy Mississippi, LLC (EML) on May 25 filed with the Mississippi Public Service Commission a petition for a certificate of public convenience and necessity (CCN) to expand and upgrade its Franklin 500-kV substation to a breaker-and-a-half bus scheme.

The company noted that it seeks a CCN to acquire, build, expand, own, operate, and maintain certain electrical facilities, including:

  • Acquiring 10 acres to expand the Franklin substation
  • Expanding 500-kV bus to the west as required
  • Installing 500-kV low and high elevation bus, switch, arrestor, and Capacitive Coupling Voltage Transformer (CCVT) supports as required
  • Installing one 500-kV line dead-end including foundations just outside of the Franklin substation
  • Installing two 500-kV circuit breakers and associated devices and equipment
  • Relocating existing conductor to new McKnight 500-kV line bay
  • Replacing breakers J2416 and J2412 and associated devices and equipment
  • Installing all related switches, arrestors, CCVTs, line traps, and control panels
  • Removing identified line panels and associated devices and equipment

The company said that it is proposing the project, located in Franklin County, Miss., in order to maintain compliance with the NERC mandatory reliability standards and to continue delivering reliable electrical service to its customers in the southwestern region of its service area. Transmission studies have identified the potential for thermal overloads in the southwest area of EML’s service territory caused by the modeled internal extra high voltage (EHV) breaker fault at the Franklin switchyard that could result in the simultaneous loss of the Franklin-Bogalusa and Franklin-McKnight 500-kV transmission lines, the company said.

EML noted that the proposed electrical facilities were identified as a solution to the identified potential transmission system limitations in the Midcontinent ISO (MISO) Transmission Expansion Process (MTEP). The proposed facilities were included in Appendix ‘A’ of MTEP 19 and subsequently approved by the MISO Board of Directors in December 2019, the company said.

EML noted that its fiber-optic network would also be extended from the Franklin substation to Entergy Louisiana, LLC’s McKnight 500-kV substation in Louisiana. The upgrades at the Franklin substation would require upgrades to the relay protection and communication systems equipment located at the McKnight substation, which is located at the remote end of the Franklin to McKnight 500-kV line and contains remote end relaying and protection equipment affecting the Franklin substation. EML said that Entergy Louisiana would perform the upgrades at the McKnight substation that are needed to address the modeled NERC contingency scenario identified as the project driver.

Among other things, the company said that the total cost of the proposed facilities is estimated to be $13.8m, and that subject to the receipt of necessary permits and required approvals, the project is planned with an in-service date of December 2022.

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