1. Page 1 ERCOT Project Status 1 ERCOT Dynamic Ratings METF March 29, 2012

2. Page 2 ERCOT Project Status Conceptual Model

3. Page 3 ERCOT Project Status Dynamic Ratings – Weather Stations and Zones

4. Page 4 ERCOT Project Status Dynamic Ratings Weather Stations to Zone Mapping

5. Page 5 ERCOT Project Status Dynamic Ratings – Real Time Process Ratings may be supplied via ICCP. Three ratings (normal, emergency, and 15 minute) must be submitted for each line. If ICCP data is not supplied or if ICCP is currently unavailable, ratings from a standard table mapped to temperatures are used. Updates are made in near real-time and applied to SCED For jointly-owned lines, the most conservative value will be used.

6. Page 6 ERCOT Project Status Dynamic Ratings Project – Look Ahead Process All lines have static temperature versus ratings tables defined by the owning TSP. All lines use the forecasted temperature of a nearby weather station (or weather zone temperature), as assigned by the TSP. ERCOT uses its 168hr weather station forecast data updated hourly by the weather vendor for both load forecasting and dynamic ratings. The resulting temperature-adjusted ratings are used for all RUC and manual future studies performed on the power system network. For jointly-owned lines or for lines that cross multiple weather stations, the most conservative value will be used.