NOTICE DATE: February 26, 2025

NOTICE TYPE: W-A022625-01 Operations

SHORT DESCRIPTION: New Hill County and nearby 345-kV (SAMSW) Generic Transmission Constraint (GTC)

INTENDED AUDIENCE: ERCOT Market Participants

DAYS AFFECTED: March 05, 2025

LONG DESCRIPTION: Results from the Sub-Synchronous Resonance (SSR) study for a planned Generation Resource included in the Quarterly Stability Assessment (QSA) in Q3 2024 indicated stability issues related to large power export out of the 345-kV transmission system in the Hill County and nearby area under prior outage conditions.  Following the SSR study, which identified potential instability issues, a GTC assessment was conducted to assess the impact of the planned Generation Resources. The evaluation concluded that a GTC is necessary to manage the stability of the 345-kV transmission system in the Hill County and nearby area. As a result, SAMSW GTC has been created in the ERCOT Network Operations Model.

The purpose of this Notice is to provide contemporaneous notification to all ERCOT Market Participants of these updates. ERCOT will begin enforcing the new Hill County and nearby 345-kV Area GTC Generic Limits on March 05, 2025.

Details associated with all GTCs (EMIL ID NP3-770-M, Report ID 11425) can be found on the ERCOT Market Information System (MIS) Grid Transmission page under the Generic Transmission Constraints Methodology Secured Area. A Digital Certificate with role ICE_M_VIEW_ECEII is required to access this ECEII data.

CONTACT: If you have any questions, please contact your ERCOT Account Manager. You may also call the general ERCOT Client Services phone number at (512) 248-3900 or contact ERCOT Client Services via email at ClientServices@ercot.com.

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