Impacts and Flexibility in Future Hub Definitions
Explore the implications of NPRR941 on Hub proposals, such as its impact on Real-Time Market systems versus Day-Ahead Market systems. Learn about the flexibility gained through NPRR817 and the identified barriers for future Hub definitions and their potential impacts. Stay updated on ERCOT's ongoing efforts to assess the effects of proposed changes.
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Discussion on NPRR941 Impacts and Flexibility for Future Hubs PRS David Maggio October 10, 2019
Current Complications NPRR941 and other Hub proposals do not significantly impact the Real-Time Market (RTM) systems. Hub prices are calculated as part of a post-process of SCED. There are no RTM transactions at the Hubs (i.e., no dispatch of injections and withdrawals). However, Hubs affect the Day-Ahead Market (DAM) more significantly, as the changes involve how a Hub is modeled, dispatched and priced. All Hubs are defined in the Network Model Management System (NMMS) with their components: group of Hub Buses. All Hub Buses are defined in the NMMS with their components: group of Electrical Buses. DAM runs on the Bus-Branch model, where Electrical Buses do not exist. Instead, DAM rebuilds the mapping between the Hub Buses and existing power flow buses, based on the model information from NMMS. The mapping is then used in DAM for dispatching Hubs, optimizing the bids and offers at Hubs, and calculating the Hub prices. 2 PUBLIC
Flexibility Gained by Implementing NPRR817 NPRR817 created a new Hub, the Panhandle Hub, but required that it not be included in the ERCOT Hub Average 345 kV Hub (HUBAVG) or ERCOT Bus Average 345 kV Hub (BUSAVG) calculations. Prior to NPRR817, it was assumed that all Hubs would be included in the HUBAVG and BUSAVG calculations. The Panhandle Hub otherwise followed the same pattern as the existing Hubs. With the implementation of NPRR817, added the flexibility to define which Hubs to include in the HUBAVG and BUSAVG calculations. 3 PUBLIC
Identified Barriers for Future Hub Definitions The impact of the following permutations are being reviewed: 1. Allow multiple/all voltage levels to be part of a Hub Bus definition. Voltage level should not limited to only 345 kV. 2. Allow the same Hub Bus (same collection of buses in the system) to be part of two different Hub definitions. 3. Allow multiple Hub Buses to be defined at the same substation, with a separate Hub Bus for each voltage level. 4. Allow a single Hub Bus to include multiple or all voltage levels at a single substation. Items 1 through 3 are part of NPRR941 4 PUBLIC
Identified Barriers for Future Hub Definitions The impact of the following permutations are being reviewed: 5. Allow separate Hubs to use the same substation differently. For example, Hub A has a Hub Bus that is just the 345 kV buses at substation X and Hub B has a Hub Bus that consist of all voltage levels as the same substation X. 6. Allow a Hub Bus to include equipment from more than one substation. 7. Allow a Hub Bus to only include a subset of a particular voltage level within a substation. 5 PUBLIC
Initial Feedback on the Impact of the Identified Barriers ERCOT is still working internally and with vendors to identify the impacts of allowing for all the identified permutations. Based on initial discussions, the most significant barrier appears to be #7. Function of the process for converting the NMMS model into a Bus-Branch model ERCOT is also considering the need to submit comments to NPRR941 that would make all Hub Bus names unique in the Protocol. This would help clarify the method of implementation and is not intended to affect the Impact Analysis 6 PUBLIC
