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Implementing CMPs for DC Tie Load

This document discusses the treatment of DC Tie Load in ERCOT operations and transmission planning, emphasizing the need for implementing Constraint Management Plans (CMPs) to avoid pre-contingency curtailments. It highlights the discrepancies between current practices and stakeholder affirmations, and suggests a policy change to prioritize DC Tie Load curtailment over transmission upgrades.

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Implementing CMPs for DC Tie Load

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  1. Implementing CMPs for DC Tie Load Shams Siddiqi, Ph.D. Representing Rainbow Energy Marketing Corporation (512) 619-3532 shams@crescentpower.net CMWG Meeting June 24, 2019

  2. DC Tie Load Pays 1.67xTCOS • 8760 flat DC Tie Load pays 1.67 times the transmission cost paid by similar other flat Load • Unlike other Load avoiding 4-CP charges, DC Tie Load cannot avoid paying this transmission charge since it’s charged in all hours as $/MWh • DC Tie Load is also allocated Ancillary Services and other costs that Loads pay • Thus, DC Tie Load should be treated the same as other Load except that DC Tie Load is shed just prior to shedding other Load – as required by current ERCOT Nodal Protocols • For ERCOT Operations and Transmission Planning purposes, DC Tie Load should be treated the same as other Load (with the exception in Emergency conditions when DC Tie Load can be shed prior to other Load, PUCT/ERCOT Protocols requiring curtailment if needed to preserve exemptions, Presidential Orders, etc. – none of these change with clarifications/directives described here) • Current practice of shedding DC Tie Load pre-contingency and SCED not pricing the corresponding constraint results in distorted prices, absence of price signals for market to respond & is inconsistent with current Protocols

  3. DC Tie Load Treatment • NPRR825 was initially drafted to revert back to ERCOT having to declare an Emergency to curtail DC Tie Load – reflecting stakeholder affirmation of treating DC Tie Load as other Load with the exceptions as noted • At ERCOT’s request, the following 4.4.4(15) was added to NPRR825 : “If market-based congestion management techniques embedded in Security-Constrained Economic Dispatch (SCED) as specified in these Protocols will not be adequate to resolve one or more transmission security violations that would be fully or partially resolved by the curtailment of DC Tie Load and, in ERCOT’s judgment, no approved Constraint Management Plan (CMP) is adequate to resolve those violations, ERCOT may instruct Resources to change output and, if still necessary, curtail DC Tie Load to maintain reliability and shall post a DC Tie Curtailment Notice to the MIS Public Area as soon as practicable. The quantity of DC Tie Load to be curtailed shall be the minimum required to resolve the constraint(s) after the other remediation actions described above have been taken.” • ERCOT position is that 4.4.4(15) “does not obligate ERCOT to develop a CMP for such transmission security violations” - it only requires ERCOT to “assess the feasibility of using approved CMPs” and that “CMPs can be proposed by others”. • This implication of ERCOT-inserted language that treats DC Tie Load very differently from other Load was not made clear when added • In NPRR405, NPRR818, and NPRR825, stakeholders have repeatedly reaffirmed the treatment of DC Tie Load as other Load except as noted in Protocols

  4. DC Tie Load Treatment • However, ERCOT is now shedding DC Tie Load pre-contingency for N-1 constraints instead of implementing a Mitigation Plan as required by NPRR825 (as we understood it) that would avoid pre-contingency DC Tie Load shed (similar to how ERCOT treats other Load) • The only difference between DC Tie Load and other Load is that DC Tie Load is shed just before other Load is shed – just because NPRR825 does not require declaring an Emergency does not imply less firm service • Thus, ERCOT should only shed DC Tie Load for base (N-0) violations and implement Mitigation Plans for N-1 constraints that shed DC Tie Load as a post-contingent action that would eliminate pre-contingency curtailments, send appropriate price signals, and incentivize economic decision making • ERCOT wanting impacted exporters to submit CMPs is unduly burdensome and very different to how CMPs are implemented by ERCOT for other Load – only recently, after months of investigation, were we able to figure out the cause of DC Tie Load shed and that CMP is a feasible solution. For each constraint, figuring out if a CMP is possible and convincing the TSP and ERCOT to work with us and implement such a CMP is very cumbersome with uncertain outcomes

  5. Planning Implications of DC Tie Load Treatment by Operations • Post-NPRR405, ERCOT Planning would plan projects for N-1 issues impacting DC Tie Load • Due to ERCOT Operations shedding DC Tie Load pre-contingency, Transmission Planning is interpreting DC Tie Load to be more like a Resource and is contemplating the following policy change: “DC tie curtailment will be utilized before proposing transmission upgrades for P0, P1, P2.1, and P7 contingencies” – a full reversal from current practice • This implies no transmission upgrades will be considered to accommodate DC Tie Load even though DC Tie Load pays much more than other Load for transmission costs and pays other costs (AS, uplifts, etc.) as well • DC Tie Load is NOT a Resource – otherwise all the provisions of make-whole payments applicable to other Resources (e.g. Switchable Generation Resources) would also apply to DC Tie Load and DC Tie Load would not be paying transmission and other load allocated costs • ERCOT Planning should continue to plan projects for N-1 issues impacting DC Tie Load

  6. NERC IRO-006-5 R1 • IRO-006-5: To ensure coordinated action between Interconnections when implementing Interconnection-wide transmission loading relief procedures to prevent or manage potential or actual SOL and IROL exceedances to maintain reliability of the bulk electric system. • Requirement R1: Each Reliability Coordinator (RC) and Balancing Authority(BA) that receives a request pursuant to an Interconnection-wide transmission loading relief procedure (such as Eastern Interconnection TLR, WECC Unscheduled Flow Mitigation, or congestion management procedures from the ERCOT Protocols) from any RC, BA, or Transmission Operator in another Interconnection to curtail an Interchange Transaction that crosses an Interconnection boundary shall comply with the request, unless it provides a reliability reason to the requestor why it cannot comply with the request. • Implications: If ERCOT receives such a curtailment request from a neighboring RC or BA, then ERCOT should comply with such request. However, if ERCOT implements CMPs (e.g. Mitigation Plans) prior to shedding DC Tie Load like ERCOT treats other Load, then there is no SOL or IROL exceedance that would require ERCOT to shed DC Tie Load pre-contingency. So, this requirement does not justify ERCOT practice of shedding DC Tie Load pre-contingency.

  7. NERC INT-006-4 R1 • INT-006-4: To ensure that responsible entities conduct a reliability assessment of each Arranged Interchange before it is implemented.. • Requirement R1: Each Balancing Authority shall approve or deny each on-time Arranged Interchange or emergency Arranged Interchange that it receives and shall do so prior to the expiration of the time period defined in Attachment 1, Column B. • 1.1. Each Source and Sink Balancing Authority shall deny the Arranged Interchange or curtail Confirmed Interchange if it does not expect to be capable of supporting the magnitude of the Interchange, including ramping, throughout the duration of the Arranged Interchange. • 1.2. Each Balancing Authority shall deny the Arranged Interchange or curtail Confirmed Interchange if the Scheduling Path (proper connectivity of Adjacent Balancing Authorities) between it and its Adjacent Balancing Authorities is invalid. • Implications: ERCOT can deny or curtail E-tag if ERCOT system is incapable of supporting that E-tag. Again, if ERCOT implements CMPs (e.g. Mitigation Plans) prior to shedding DC Tie Load like ERCOT would for other Load, then the grid is capable of supporting E-tags up to the physical tie limit in almost all cases. So, this requirement does not justify current ERCOT practice of curtailing DC Tie Load pre-contingency and unequal treatment from other Load.

  8. Conclusion • In negotiating a compromise with ERCOT in NPRR825, ERCOT made clear that DC Tie Load would not be treated any differently with ERCOT issuing DCTCN instead of declaring an Emergency prior to shedding DC Tie Load • NPRR825 requires that ERCOT exhaust SCED congestion management, RUC and CMPs prior to shedding DC Tie Load similar to how ERCOT would treat other Load • ERCOT position that 4.4.4(15) “does not obligate ERCOT to develop a CMP for such transmission security violations” was not made clear during NPRR825 process and contradicts repeated affirmations by Stakeholders to treat DC Tie Load as other Load to the greatest extent allowed • Can Stakeholders direct ERCOT to implement Mitigation Plans that curtail DC Tie Load only if required as post-contingent action (preferred) or do we need to file yet another Urgent NPRR to clarify this (would like to avoid)? • ERCOT Planning should continue to plan projects for N-1 issues impacting DC Tie Load

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