The Impact of Ice Nebraska Public Power District

2 Christmas Storm Outcome 10 transmission lines out – made temporary repairs to 8 – 2 remained out of service 4 telecommunications fibers inoperable – no telecommunications west of Holdrege 2,500 retail customers impacted 21 NPPD technicians assist Dawson PPD $1.0 Million in damages (approximate)

3 New Year’s Storm Timeline Friday – December 29 Rain, freezing rain, icing, wind Saturday – December 30 Severe icing conditions and wind Widespread, extensive damage Crews respond to numerous outages Sunday – December 31 Major effort to assess damage and restore power

Back-to-Back Storms Christmas Storm:New Year’s Storm:

5 Normal NPPD Transmission System

6 System Condition January 1

7 System Condition January 4

8 Kearney Area Damage Assessment # # -Wood Structures-Steel Towers # -Shield Wire Miles

9 Early Priorities Kearney –Lost 4 of 5 transmission feeds –Priority restoration of second feed –Rolling blackouts during initial restoration Holdrege –Lost all 3 transmission feeds –Mobile generation located within the community Key Messages –Energy conservation –Fragile system –Safety

10 System Status – March 2, 2007 Initial Current Miles assessed 2,650 Customers without power –NPPD Retail (service restored: 1/6/07) 11,6120 –Wholesale customers 31,000 0 (service restored: 1/19/07) Transmission System (approx, 71% repaired) –Number of line segments out 37 7 –Transmission miles out-of-service 1, –Number of substations out 180 –Miles of conductor down –Number of structures damaged 1, GGS east flow limitation 224 MW 990 MW Communities on Mobile Generators 14 0 More than a dozen public power utilities impacted by storm Contractors on site throughout reconstruction *These MW will depend on transmission system status, loading conditions and regional transmission system conditions. Up to

11 FEMA Disaster Declaration FEMA-1674-DR

12 Ice on a guy wire

13 Engineering Design Criteria National Electrical Safety Code 1997 –Heavy combined ice and wind loading, ½ inch radial ice, 40 mph wind, 0°F National Electrical Safety Code 2007 –Heavy combined ice and wind loading, ½ inch radial ice, 60 mph wind, 15°F New Year’s storm –2 inch radial ice, winds averaging 21 mph, gusts up to 40 mph, temperatures hovering around freezing

14 Effect of Ice on Power Lines Typical weight of conductors without ice – ½ to 1 pound per foot Weight of lines with ice can increase by pounds per foot Weight on structures increased up to times after ice storm –Example: 115kV structure load went from 3,000 pounds to 26,000 pounds (2-inch radial ice)

15

16 Size of ice one week after storm

The ice mangled 345-kilovolt structures like twist-ties

18 More than 40, 345-kilovolt structures were destroyed

19 The storm snapped H-frame structures like twigs

20 More than 300 miles of line and 1,137 structures were damaged

21 Ice on Substation near Holdrege, Neb.

Emergency Restoration

23 Initial Response Public Safety –Cleared roadways –Public Service Announcements –Coordinated Emergency Personnel –Coordinated with Governor’s Office –Coordinated with Nebraska Emergency Management Agency (NEMA) and Federal Emergency Management Agency (FEMA) Employee/Contractor Industrial Safety –Reinforced NPPD Safety policies –Cognizant of portable generators

24 Initial Response Assessed damage to transmission infrastructure –Surveyed more than 1,900 miles of line; using helicopters from Air National Guard, Nebraska Highway Patrol and a private flying service Ensured Nebraskans had power –Needed to energize 115kV substations Restore transmission feeds to hardest hit communities which lost multiple transmission feeds Energize distribution system to end-use customers Site mobile generation (NPPD, NEMA, FEMA) Assist other utilities as resources permit Restore telecommunications capability

25 Emergency mobile generation was brought in for 14 communities

26 Mutual aid near Elgin, Neb.

Day-after-day diligence for more than 30 days. The last community on emergency generation was restored line service on Jan. 29, 2007.

Reconstruction

29 Reconstruction Strategy Reconnect Nebraska electrically west to east Secure contracts and labor resources to safely expedite rebuilding transmission system network –Align reconstruction contractors based on capability, line criticality and proven performance –Align contractors, mutual aid workers and District employees with performance expectations

30 Restore Transmission System Material procurement and delivery Focus on primary reconstruction efforts Hire and assign contractors Parallel efforts (Customer Service Priorities) System Network Priorities Watch the weather Ensure equipment functions

32 More than 3,000 wood poles ordered.

33 Unloading conductor at NPPD’s York Operations Center for miles of line

34 Contractors Reconstructing South of Holdrege, Neb.

35 Restoration efforts near Prosser, Neb.

36

37 Long-Term Challenges Maintaining electric grid reliability with weakened high-voltage transmission system Reconstructing during winter months (possibility for additional storms) Repairing electric grid in time for irrigation season and peak summer electric load Ensuring timely material deliveries; managing multiple, concurrent projects Restoring normal generation output from Gerald Gentleman Station

38 Major Impacts Over 200 Union Pacific trains stopped due to downed lines across rails and loss of power to central signal control Multiple Fiber Breaks –Hildreth to Holdrege –Holdrege – J2 –Axtell – Holdrege –Crooked Creek – Riverdale –Riverdale - GI

39 New Year’s Ice Storm Area 39 Transmission Lines Out-of-Service

40 Generators at Holdrege

41 Loads on Line Supports Force TOP VIEW Typical Failure Point Tension Transverse Tension

42 “(This storm) was the greatest catastrophe to ever hit a Nebraska utility. It will be remembered and talked about for lifetimes.” Comment describing March 29,1976 ice storm from NPPD commemorative booklet.