1. FREQUENCY LIMITS R-BC Workshop FREQUENCY LIMITS WECC PWG August 13, 2009

2. Determining Frequency Limits for WECC First step of UFLS in WECC Determine average frequency-response in WECC Identify Most Severe Single Contingency events Determine the low Minimum Safe Megawatt Deadband for WECC

3. Frequency Observations in WECC

4. Frequency Response in WECC

5. Frequency Limits Frequency Relay Limit High60.5 Hz Frequency Abnormal Limit High60.2 Hz Frequency Trigger Limit High60.068 Hz (60.075 Hz) Frequency Trigger Limit Low59.932 Hz (59.856 Hz) Frequency Abnormal Limit Low59.8 Hz (59.722-59.943 Hz) Frequency Relay Limit Low59.5 Hz

6. CPS1 and BAAL Operating Ranges

8. Questions ?