February 26, 2013Board of Directors Meeting

Event UpdateFourth Quarter 2012

2

4th Quarter 2012 Events

4th Quarter 2012 Event and Compliance Monitoring Report

23

3

Events - 4th Qtr

Cat 0

Cat 1

Cat 2

Cat 3

Cat 4

4% 4%4%

88%

Event Cause - 4th Qtr

Equipment Failure

Sabotage

Cyber Security

Weather

Relaying Issues

Unit Trips > 450 MW (Mult. Causes)

3

2012 Events

4th Quarter 2012 Event and Compliance Monitoring Report

81

24

1

2012 Events

Cat 0

Cat 1

Cat 2

Cat 3

Cat 4

2% 2% 1%6%

2%

86%

2012 Event CausesEquipment Failure

Sabotage

Cyber Security

Weather

Relaying Issues

Unit Trips > 450 MW (Mult. Causes)

4

NERC Event Category Examples

4th Quarter 2012 Event and Compliance Monitoring Report

● Category 1 - unexpected loss of 3 or more BPS elements contrary to design; failure or misoperation of SPS/RAS; unplanned evacuation from BPS control center facility with BPS SCADA for 30 minutes or more; loss of generation of 1000-1300 MW in ERCOT Interconnection; etc.*

● Category 2 - loss of all BPS control center voice or SCADA, control, or monitoring functionality for 30 minutes or more; unintended loss of 300 MW or more firm load for > 15 minutes; loss of off-site power to nuclear generating station, violation of IROL for > Tv; unintended system separation resulting in island of 1000-4999 MW, etc.*

● Category 3 - loss of 1,400 MW or more in ERCOT Interconnection or unintended system separation resulting in an island of 5,000 MW to 10,000 MW*

● Category 4 - loss of load or generation from 5,001 MW to 9,999 MW, or unintended separation resulting in an island of more than 10,000 MW*

● Category 5 - loss of load or generation of 10,000 MW or more*

● Category 0 - events below the above thresholds, such as SPS activations, useful for trending purposes.