NOTICE DATE: July 11, 2025

NOTICE TYPE: W-A022625-02 Operations

SHORT DESCRIPTION: Update Regarding Application of Hill County and Nearby 345-kV (SAMSW) Generic Transmission Constraint (GTC)

INTENDED AUDIENCE: ERCOT Market Participants

LONG DESCRIPTION: As detailed in Market Notice W-A022625-01, ERCOT established a new Hill County and Nearby 345-kV (SAMSW) Generic Transmission Constraint (GTC) on March 5, 2025 to address a stability risk associated with weak grid conditions that occur during certain multiple contingency scenarios. 

Based on further evaluation of this stability issue, ERCOT has determined that allowing any additional transmission-level, inverter-based generation that has not currently received Part 2 approval to synchronize to the Transmission Grid in this area would create an unacceptable risk to system stability irrespective of the level of dispatch.  Consequently, ERCOT is providing this additional notice that, until further notice, any Interconnecting Entity proposing to connect any new inverter-based generator at transmission voltage in the area subject to the GTC, including any such generator that has already begun the Generator Interconnection or Modification process, will, as a condition for part 2 approval, be required to (1) fully mitigate any stability risk associated with the interconnection or operation of the generator and (2) obtain confirmation of the effectiveness of the mitigation solution through an ERCOT or TSP study. 

ERCOT is currently evaluating possible transmission upgrades that are expected to allow for exiting the GTC.  Once a potential exit strategy is identified, ERCOT will incorporate the strategy into the SAMSW GTC methodology and will post the revised methodology to the ERCOT MIS Secure Area, in accordance with Paragraph (7) of Protocol Section 3.10.7.6. 

The purpose of this Market Notice is to provide contemporaneous notice to all ERCOT Market Participants of these updates.   ERCOT will issue a subsequent Market Notice once it determines that the interconnection conditions described in this Market Notice are no longer necessary. 

Details of 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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