1. Review of TADS Data for 2012 Voltage Class Name Metric AC Transmission Outages - Failed Protection System Equipment AC Transmission Outages - Human Error AC Transmission Outages - Failed AC Substation Equipment AC Transmission Outages - Failed AC Circuit Equipment AC Transmission Outages - Lightning AC Transmission Outages - Contamination AC Transmission Outages - Foreign Interference Total Element Availability Percentage (APC) Transmission System Unavailability AC Circuit 300-399 kV Outages per Circuit0.02620.042600.05890.04580.20130.09900.06070.734898.61921.3808 AC Circuit 300-399 kV Outages per 100 miles per year0.08040.13070.18090.14070.63330.31160.19102.3121 300-399 kVJan-12Dec-12 # Circuits310316 Circuit Miles9845.610049.4 Multi-circuit Structure Miles2755.32970.3 Automatic Outages Circuit Data Outage InformationCountDuration (hrs) Automatic230682.6 Non-Automatic51636295.1 Outage Data Outage InformationCount Duration (hrs) Two Elements94.82 Three Elements35.3 Four or More Elements118.3 Multiple Element Automatic Outages

2. Review of TADS Automatic Outage Data for 2012 ●Lightning, Contamination, and Unknown represent 73% of all momentary outages ●Momentary and Sustained automatic outages by month for 2012

3. Review of TADS Automatic Outage Data for 2012 ●Failed AC Substation Equipment represented 22% of sustained outage cause vs. 46% of sustained outage duration ●Failed AC Circuit Equipment represented 7% of sustained outage cause vs. 16% of sustained outage duration

4. Review of TADS Planned Outage Data for 2012

5. ●55% of planned outage duration ranges from two to 24 hours ●37% of planned outage duration is greater than 24 hours

6. TADS Comparison, 2011 vs 2012 20112012 Outage InformationCountDuration (hrs)CountDuration (hrs) Automatic2791908.6230682.6 Non-Automatic78746712.451636295.1 2011201220112012 Voltage Class 300-399 kV MetricOutages/Number of circuitsOutages/100 mi/year AC Transmission Outages - Failed Protection System Equipment 0.03050.02620.09260.0804 AC Transmission Outages - Human Error 0.06770.04260.20570.1307 AC Transmission Outages - Failed AC Substation Equipment 0.13200.05890.40110.1809 AC Transmission Outages - Failed AC Circuit Equipment 0.05080.04580.15430.1407 AC Transmission Outages - Lightning 0.20670.20550.63760.6333 AC Transmission Outages - Contamination 0.16670.10110.51420.3116 AC Transmission Outages - Foreign Interference 0.05670.06200.17480.1910 Total 0.93000.75042.86942.3121 Element Availability Percentage (APC) 98.062598.6192 Transmission System Unavailability 1.93751.3808

7. TADS Comparison, 2010-2012

8. TADS Comparison, 2008-2012 April-May 2011 had higher than normal rate of contamination-related outages due to ongoing drought issues Sept 2011 had high sustained outage duration due to wildfires

9. Common Mode and Dependent Mode Outage Statistics 2010-2012 Dependent Mode outages (defined as an automatic outage of an element which occurred as a result of another outage) Common Mode outages (defined as one or more automatic outages with the same initiating cause and occur nearly simultaneously) In 2012, represented 6.0% of all momentary outages, 26.3% of all sustained outages (6.6% of sustained outage duration), and 13.0% of all automatic outages.

10. NERC Adequate Level of Reliability (ALR) Metrics 201020112012 MetricDefinitionERCOT Metric NERC Metric ERCOT Metric NERC Metric ERCOT Metric NERC Metric ALR6-11Automatic Outages Initiated by Failed Protection Equipment 4.95%6.26%3.05%5.55%2.62%5.07% ALR6-12Automatic Outages Initiated by Human Error 1.41%6.57%6.77%6.87%4.26%6.55% ALR6-13Automatic Outages Initiated by Failed AC Substation Equipment 8.13%5.59%13.2%8.14%5.89%6.19% ALR6-14Automatic Outages Initiated by Failed AC Circuit Equipment 2.83%5.89%5.08%5.37%4.58%4.78% ALR6-15Element Availability Percentage 98.64%98.41%98.06%97.86%98.62%97.89% Comparison of ERCOT to NERC metrics for Adequate Level of Reliability measurements