1. ERCOT Drought Best Practices Workshop Contamination Issues February 27, 2012

2. 2 2/27/2012 Insulator Flashover Events In April 2011 TNMP began to experience insulator flashover events in stations in the Texas City industrial area. Caused by industrial and saline contamination combined with record drought. The faults caused customer equipment to trip, resulting in plant shutdowns and flaring. As the drought continued, flashovers also occurred on transmission lines, and then eventually distribution lines.

3. 3 2/27/2012 Insulator Flashover Events

4. 4 2/27/2012 TNMP Response Transmission Switching stations were hand cleaned or power washed and treated with silicone sealant. Most of the transmission lines in the Gulf Coast region were power washed using Company crews and helicopter crews. Distribution lines in the Industrial area were power washed using Company and contractor crews.

5. 5 2/27/2012 TNMP Response

6. 6 2/27/2012 TNMP Revised Practices - Monitoring During the incidents of Spring and Summer 2011, TNMP used early morning UV and IR monitoring to ID potential problem areas. Survey results used to prioritize station and line washing. Additional UV and IR equipment purchased and personnel trained in use and interpretation.

7. 7 2/27/2012 TNMP Revised Practices - PM TNMP has revised its PM practices in response to the flashover events and lessons learned as we responded. In addition to annual PM surveys, UV and IR surveys now triggered by 1 mo. of no rainfall. Early morning UV and IR Surveys. Positive UV findings trigger station or line equipment power washing.

8. 8 2/27/2012 UV Inspection Results

9. 9 2/27/2012 Questions