CALDWELL, Texas (KRHD) — The city of Caldwell is transitioning from the Midcontinent Independent System Operator electric grid to the Electric Reliability Council of Texas grid, citing an aging substation and the need for more reliable service as the city expands.
The transition is scheduled to begin March 12, and city officials warn that service disruptions are possible but should not last longer than an hour.
Caldwell's existing substation is 57 years old and serves more than 2,000 retail electric meters, primarily within the city's municipal boundaries in Burleson County. The substation's transformer is 35 years old and has experienced performance issues, including at least one failure related to its load tap changer. City officials say the substation would require extensive and expensive upgrades to remain in service.
The city currently receives electric transmission service through Entergy Texas and operates approximately 65 circuit miles of distribution lines throughout Burleson County. Because the existing substation occupies its entire property footprint, there is no room to make the necessary upgrades at the current site.
Rather than rebuild at or near the existing location, Caldwell chose to connect to a new substation that will tie into LCRA Transmission Services Corporation's Cooks Point 138-kilovolt transmission line, which runs through the city's municipal boundaries and certificated service area. The Cooks Point Line was built in 2021 on storm-hardened steel or concrete structures and operates at a higher voltage than the current 69-kilovolt lines serving Caldwell.
The city's current grid position — on the far western edge of the MISO system — has historically made it vulnerable to service interruptions. Caldwell experienced a five-day outage during Hurricane Ike, which officials cited as an example of the reliability risks associated with its current grid connection.
The new substation will be constructed, owned, and operated by LCRA TSC. It will initially include a single 138-kV power transformer, with space reserved for a mobile transformer connection and a second power transformer to support future growth. The new configuration is also designed to allow for a more reliable ring bus setup at a later date.
To complete the transition, crews will disconnect Caldwell's load from the existing MISO substation before connecting it to the new ERCOT substation. The process will include opening distribution breakers, removing primary wire from all four feeder bays, and creating a physical separation of approximately 20 feet between Caldwell's facilities and any equipment still connected to MISO. The switchover will be coordinated with ERCOT, LCRA TSC, and Entergy.
Both MISO and ERCOT conducted reliability studies ahead of the transition. MISO found that removing Caldwell's load — currently 14 megawatts — would cause no thermal or voltage violations on its system. LCRA TSC's facility interconnection study similarly found no new thermal or voltage criteria violations resulting from the load addition to ERCOT. LCRA TSC also confirmed the system can support up to 17 MW of load for Caldwell.
The Public Utility Commission of Texas approved the transfer following an application filed by the city in early 2024.
Entergy's facilities at the existing substation will remain in place and continue to serve Entergy's customers in the area. The transition is not expected to affect Entergy's operations, and officials say freeing up space at the substation site could benefit Entergy's future expansion needs.
The new substation may also benefit other utilities in the area. Bluebonnet Electric Cooperative, which serves customers in the surrounding region, would be able to connect feeders to the new substation, potentially improving voltage levels and reducing line losses for customers across the area.
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