Load Distribution Factor Calculation for Market Applications and Studies a Presentation for NATF 9/21/2010 - NATF 1 Texas Nodal

Load Distribution Factors Nodal Protocols state in section 4.5 – Dam Execution and Results (5) ERCOT shall determine the appropriate Load distributions to allocate offers, bids, and source and sink of CRRs at a Load Zone across the Electrical Buses that are modeled with Load in that Load Zone. The default distribution is the State Estimator hourly distribution for the seven days before the Operating Day. If ERCOT decides, in its sole discretion, to change this distribution for reasons such as anticipated weather events or holidays, ERCOT shall select a State Estimator distribution from a proxy day reasonably reflecting the anticipated distribution in the Operating Day. ERCOT may also modify this distribution to account for predicted differences in network topology between the proxy day and Operating Day. ERCOT shall develop a methodology, subject to Technical Advisory Committee (TAC) approval to describe the modification of the proxy day bus-load distribution for this purpose. 2 Texas Nodal

ERCOTs Proposal ERCOT has concluded from the results of the market trials, that it is advisable to open the nodal DAM market using a stable set of bus-load distribution factors in place of the state estimator hourly distribution from 7 days prior to the operating day. Use of filtered load distribution factors from 7 days previous allows telemetry errors to propagate into the DAM model Through capture and testing of LDF’s for a proxy day, ERCOT can reduce or eliminate unexpected DAM results caused by load distribution factors. ERCOT intents to open the market using a set of static, tested Load distribution factors. ERCOT will capture state estimator results from a “proxy” day, and test these LDF’s with sample DAM executions in the lab with “typical” bid information. ERCOT will examine the results, and iterate with adjusted distributions where unreasonable load distributions result. ERCOT will utilize these “proxy” distributions for each day of the target month, or until revisions are required. 3 Texas Nodal