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NPRR #1034 · Revision Request

NPRR1034  Frequency-Based Limits on DC Tie Imports or Exports

Approved sponsor Southern Cross Transmission posted 2020-07-22 ercot.com
ReasonRegulatory requirements: This NPRR is proposed in accordance with the May 23, 2017, order of the Public Utility Commission of Texas (PUCT) in Project No. 46304, Oversight Proceeding Regarding ERCOT Matters Arising Out of PUC Docket No. 45624 Relating to DC Tie Project Proposed by Southern Cross Transmission, LLC, which requires ERCOT to address a number of issues as a condition for the energization of the DC Tie project proposed by Southern Cross Transmission LLC (“Southern Cross Transmission”). As proposed, the Southern Cross DC Tie would be capable of importing 2,000 MW or exporting 2,100 MW. The PUCT’s Directive 9 in the order requires ERCOT to “evaluate what modifications to existing and additional Ancillary Services, if any, are necessary for the reliable interconnection of the Southern Cross DC tie.” ERCOT’s studies evaluating the potential need for Ancillary Services associated with the Southern Cross DC Tie identified a risk of unacceptable frequency overshoot in the event of the loss of the Southern Cross DC Tie when exporting above certain levels under certain operating conditions. ERCOT’s evaluation further identified likely future procurement of incremental Ancillary Services as a means to address the frequency overshoot concern. Southern Cross Transmission proposes this NPRR as a more efficient solution for the entire market by establishing limits on certain DC Tie transfers when necessary to address the risk of frequency overshoot, rather than requiring procurement of additional Ancillary Services.
Created2020-08-13
Approved2021-02-09
Sections Affected
4.4.4 and 4.4.4.3 (new)
Summary
This Nodal Protocol Revision Request (NPRR) creates new Protocol Section 4.4.4.3, Frequency-Based Limits on DC Tie Imports or Exports to allow ERCOT to establish import or export limits on Direct Current Ties (DC Ties) to avoid the risk of any unacceptable frequency deviation that may be identified in the event of an unexpected loss of one or more DC Ties when importing or exporting. Revisions to Section 4.4.4, DC Tie Schedules, would allow ERCOT to curtail DC Tie Schedules on a DC Tie on a last-in-first-out basis when necessary to address this risk. The last-in-first-out curtailment methodology is consistent with current practice documented in the ERCOT DC Tie Operating Procedure Manual. ERCOT would be required to post on the Market Information System (MIS) Public Area the operating conditions and associated limits that it would expect to use.
Timeline