Marion-Conway 230kV Line

The Marion – Conway 230kV Line transmission project includes constructing a new approximately 34-mile 230kV line by rebuilding an existing 115kV transmission line as double circuit via exiting right-of-way.  

Santee Cooper transmission planning assessments have identified thermal loading and voltage violations under contingency conditions in the eastern region of the transmission system that are mitigated by the addition of a Marion – Conway 230kV line. These thermal loading exceedances do not meet the transmission system planning performance requirements under NERC Reliability Standard TPL-001-5 or Santee Cooper’s internal planning criteria. Potential violations may occur as early as June of 2025.

The thermal and voltage violations described above could pose serious risk to the transmission system reliability in the area and result in the need to curtail large amounts load if this line is not constructed. To provide the necessary thermal loading relief and voltage support to the transmission system, the construction of the Marion – Conway 230kV Line is needed. This 230 kV line will also provide an additional source for a highly concentrated load area of the Santee Cooper system that continues to see significant load growth.

Santee Cooper plans to utilize approximately 34-miles existing right-of-way to minimize environmental and cost impacts. Utilizing existing right-of-way also allows for an older 115kV line to be upgraded to current design standards, increasing resiliency during extreme weather events and supports additional load growth.

The double circuit 230/115 kV line rebuild sections will replace old wooden poles with single pole steel structures. 

In March 2022, we contacted property owners by letter to make them aware of the upcoming construction. We are working with those who have encroachments in the easement to make sure the right of way is clear. Clearing began in April 2022.

You can contact us at transmissionprojects@santeecooper.com.