CRR; Operations

Wed, Feb 17, 2021 09:54 AM

M-A021721-01 Proposal to Retire Culberson Loop RAS

NOTICE DATE: Februray 17, 2021

NOTICE TYPE: M-A021721-01 Operations

SHORT DESCRIPTION: Proposal to Retire Culberson Loop Remedial Action Scheme (RAS)


DAYS AFFECTED: Feburary 24, 2021

LONG DESCRIPTION: ERCOT has received a proposal from Oncor Electric Delivery Company LLC (Oncor) to retire the Culberson Loop Remedial Action Scheme (RAS). The Culberson Loop RAS consists of redundant relays placed at every transmission switching station, wired to monitor the status of each transmission line terminal on the Culberson Loop. Under specific system configurations, voltage instability can occur. The RAS automatically performs remedial tripping in response to the specific contingencies of concern. Oncor has indicated that the RAS is no longer required because the contingencies of concern do not result in voltage instability, due to 345kV transmission upgrades in the area.

The proposal to retire the Culberson Loop RAS is being reviewed by ERCOT.

ACTION REQUIRED: Comments to this proposal are due to ERCOT by 5:00 pm on Feburary 24, 2021, and should be submitted to using the attached comment form. Any questions or concerns submitted by this date will be addressed by ERCOT or Oncor.

ADDITIONAL INFORMATION: Information regarding all RASs can be found in the “Remedial Action Schemes and Constraint Management Plans” secure portlet located on the Market Information System (MIS) under the Transmission page of the Grid section.

Please review the ERCOT website for previous Market Notices related to the subject.

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

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Culberson_Loop_RAS_Comment_Form.docx (Feb 17, 2021 – docx)