State Estimator (SE) and Simultaneous Feasibility Test (SFT) Status Report Steve Myers Manager of System Operations

State Estimator  Progress Total difference between generation & load reduced from 10’s of 1000’s at first to <500 MW Approximately 25 buses >50 MW mismatch 90% observability (75% with measurements)

Uses of the State Estimator  Identifying data problems  Identifying model problems  Monitoring of locations w/o SCADA (by System Operators)  Creating a case for Contingency Analysis Normally successful at least once per day

SE Plan  Continue to incrementally improve  Continue to reduce mismatches  With Engineer’s attention, use in Day-Ahead analysis  Train System Operators  Ultimately – SE will run CA in RT sequence

SE Plan  Needs Data Response from QSE’s and Private Networks Unit Status – QSE Private Network Issues to Correct Net Gen sent as one unit Loads not modeled Data required by ERCOT Operating Guides Section 8

Simultaneous Feasibility Test (SFT)  Calculates “Shift Factors” used in Congestion Management  Progress Attempted use in December '02 Bugs that had not shown up in test mode Waiting on fixes from vendor Once offline testing complete, will test again in production

SFT Plan  Use in Day-Ahead Initially peak hour Limited contingencies  Use in Hours Ahead Initially test mode Limited contingencies Limited iterations with SPD

Next Steps  Contingency Analysis will run in the Real- Time sequence and upon demand  SE and SFT will run for each BES deployment  ERCOT expects its systems to be ready By April 1

What Do We Gain?  More accurate analyses – closer to RT  Greatly improved pro-active CM  Much more accurate “Shift Factors”  Potentially less OOM deployments