NPRR712  Clarification of RUC Process

This Nodal Protocol Revision Request (NPRR) is submitted to clarify certain language regarding the Reliability Unit Commitment (RUC) process. Section 6.4.7.2, QSE Request to Decommit Resources in the Adjustment Period, requires a Qualified Scheduling Entity (QSE) that chooses to decommit an otherwise available Resource, for hours other than the Operating Period, to update the Current Operating Plan (COP) indicating the change in Resource Status for future hours. The RUC process detects the change in COP status from On-Line to Off-Line Available in the future hours as a request for decommitment, and ERCOT is required to review all such decommitment requests during each Hourly RUC (HRUC) sequence. Section 6.4.7.2 also requires that “The Resource must be shown as available for HRUC commitment.” This requirement has resulted in confusion among some QSEs, especially when reporting the COP status for a Generating Resource having a start-up time of one hour or less. Since the HRUC process normally begins soon after the end of the Adjustment Period (although ERCOT has discretion to execute the HRUC process at any time), QSEs with these relatively short lead time Resources must make a decommitment decision over 2 hours in advance of a particular Operating Hour, otherwise the updated COP will not show the Resource as “available for HRUC commitment” in that Operating Hour, resulting in a potential violation of Section 6.4.7.2. Compliance issues can also occur because QSEs are never exactly sure when ERCOT will initiate the HRUC process. While it is generally ERCOT’s practice to begin the HRUC process only a few minutes after the end of the Adjustment Period, as mentioned above ERCOT has discretion to execute the HRUC process at any time. Therefore, Resources with a start-up time of only 30 minutes, for example, which have been decommitted through a status change in the COP, may inadvertently make the Resource unavailable for RUC commitment if the RUC process doesn’t begin until 30 minutes after the end of the Adjustment Period. Exacerbating this potential compliance issue, ERCOT Staff has described the RUC algorithm as having a “15 minute buffer” that is added to the start-up times of all Resources to account for the time it takes to execute the RUC process. This 15 minute buffer effectively places all Resources, but especially those having a start-up time of one hour or less, at risk of violating the Section 6.4.7.2 requirement to show all decommitted Resources as “available for HRUC commitment,” because QSEs have not been aware of the 15 minutes being added to Resource start-up times. To resolve these RUC and COP timing issues, ERCOT Staff has stated their intention to modify the HRUC process and provide a list to the ERCOT Operators of all Off-Line Available Resources having a start-up time of one hour or less. This will allow QSEs with such Resources to update their COPs accurately and avoid a possible compliance issue by allowing a decommitment decision to be made just prior to the end of the Ajustment Period. The list of Off-Line Available, one hour or less start-up time Resources effectively makes the Resources “available for HRUC commitment,” even if the RUC software cannot commit them during the Operating Period due to the start-up time constraint and the 15 minute buffer inherent in the RUC software. Language is included in this NPRR to describe this proposed process change. Clarification is also needed regarding when a RUC-committed Resource must be on-line and released to Security-Constrained Economic Dispatch (SCED). Based on discussions with various QSEs, some believe a RUC-committed Resource should be on-line and released to SCED “prior to” the start of the RUC committed hour, while others believe the Resource must only be on-line and released to SCED “during” the RUC-committed hour. Exacerbating the confusion, the current language contained in Section 8.1.2, Current Operating Plan Performance Requirements, does not appear to meet the intent of a RUC deployment, as this section deems a Resource as “passing” the performance metric if the Resource is “On-Line and released to SCED for deployment in the RUC-Commitment Hour.” (emphasis added). As an extreme example, a RUC-committed Resource would pass the metric even if it was only released to SCED for a single minute in the commitment hour, which is clearly not the intent of an hour long commitment instruction. Language has therefore been added to Section 8.1.2, Current Operating Plan Performance Requirements, suggesting that all RUC-committed Resources be on-line and released to SCED within the first 15 minutes of a RUC deployment instruction.