NPRR #277 · Revision Request
NPRR277 Removal of NPRR119 Language for LDL Calculation and Modification to the SCED Ramp Rate Calculation (formerly "Removal of NPRR119 Language for LDL Calculation")
ReasonThe change to LDL calculation that was part of NPRR119 was intended to ensure that the Resources could not be dispatched at a level above the telemetered High Sustainable Limit (HSL). An unintended consequence of this change is that Security-Constrained Economic Dispatch (SCED) is able to set Base Points for a Resource that may not be attainable according to the ramp rates provided for that Resource. The ramp rates being used are either the Resource Asset Registration Form (RARF) ramp rates or those submitted via the Market Participant User Interface. If a large number of Resources are unable to follow Base Points, it may be difficult for ERCOT to match Load and generation and thus maintain frequency. This NPRR should help ensure that the all Base Points produced by SCED are attainable within the next five minutes. In addition, this change will mitigate ERCOT’s sensitivity to the HSLs that are being telemetered by the Qualified Scheduling Entities (QSEs) and will place a larger degree of dependency on telemetered net MW and the ramp rates that have been provided for the Resource. This is in line with ERCOT’s RLC design approach which gives the telemetered net MW output highest priority in instances in which there are telemetry quality and/or accuracy issues. These changes also ensure that at least some ramp capability is available from each Resource to SCED to economically resolve constraints.
Created2010-09-23
Approved2010-11-16
Sections Affected
6.5.7.28.1.1.4.1
Summary
This Nodal Protocol Revision Request (NPRR) removes changes that were made to the Low Dispatch Limit (LDL) calculation within the Resource Limit Calculator (RLC) as part of NPRR119, Resource Limit Calculator. The language in this NPRR will ensure that a Resource’s Dispatch limits are calculated taking into consideration the Resource’s current net MW output and ramp rates. This NPRR also changes the Security-Constrained Economic Dispatch (SCED) Up and Down Ramp Rate calculation (SURAMP and SDRAMP) to reduce the amount of ramp rate that is reserved for Regulation Service.
Action Log 4 milestones
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Sep 23
PRSRecommended for Approval→ PRS IA Review
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Oct 21
PRSRecommended for Approval→ TAC Consideration
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Nov 4
TACRecommended for Approval→ ERCOT Board Consideration
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Nov 16
BOARDApproved
Amendments
| Date | Body | Motion | Result |
|---|---|---|---|
| Sep 23 '10 | PRS | To recommend approval of NPRR277 as revised by PRS | Passed |
| Nov 4 '10 | TAC | To recommend approval of NPRR277 as amended by the 11/3/10 ERCOT comments | Passed |
Documents 9
| Name | Type | Posted | Classification |
|---|---|---|---|
| 277NPRR-01 Removal of NPRR119 Language for LDL Calculation 09161 | doc | Sep 16 '10 | Revision Request |
| 277NPRR-02 CEO Revision Request Review 091610 | doc | Sep 16 '10 | Revision Request Comments |
| 277NPRR-03 Impact Analysis 091610 | doc | Sep 16 '10 | Staff Report |
| 277NPRR-04 Luminant Comments 092010 | doc | Sep 20 '10 | Revision Request Comments |
| 277NPRR-05 PRS Report 092310 | doc | Sep 28 '10 | Committee Report |
| 277NPRR-06 PRS Report 102110 | doc | Oct 26 '10 | Committee Report |
| 277NPRR-07 ERCOT Comments 110310 | doc | Nov 4 '10 | Revision Request Comments |
| 277NPRR-08 TAC Report 110410 | doc | Nov 5 '10 | Committee Report |
| 277NPRR-09 Board Report 111610 | doc | Nov 19 '10 | Committee Report |
Meetings That Took It Up 3
| Date | Meeting | Committee | Status |
|---|---|---|---|
| Nov 4 '10 | TAC Meeting | TAC | Concluded |
| Oct 21 '10 | PRS Meeting | PRS | Concluded |
| Sep 23 '10 | PRS Meeting | PRS | Concluded |