1. NW Loss of Load Probability James Gall Power Supply Analyst james.gall@avistacorp.com 509.495.2189

2. LOLP Approach  Anchors on Avista’s 2005 Integrated Resource Plan  Uses AURORA XMP version 7.5.0.43 regional database and functionality  Studies 1 st and 3 rd week of January 2007  Simulates 2,000 iterations with variances in load, hydro, and thermal & transmission forced outages

3. Western Interconnect Topology Northwest Areas

4. Northwest Demand Distribution  All zones within AURORA XMP have a demand distribution  Each area is assigned a mean, co- variance (Stdev/mean) and a correlation to the Northwest  For modeling purpose each zone assumes a normal distribution  Co-variance and correlation statistics can be found in the 2005 Avista IRP, and are based on recent FERC 714 forms

5. Northwest Hydro Distribution 26%92%59%  Northwest, S. Idaho, Montana, and British Columbia each have a distribution of hydro energy  Mean and covariance statistics are based on the NWPP 2003-04 regulation hydro study (1928- 1988)  For modeling purposes hydro is assumed to be normally distributed based on the options available to be modeled within AURORA XMP Lowest Regional Year 1932: 37.7% Lowest Northwest Year 1945: 32.5% Highest Year 1974: Regional: 87.3%, Northwest: 83.1%

6. Northwest Thermal Distribution  Each thermal unit in the Western Interconnect has a forced outage rate (FOR) and mean time to repair (MTTR) assigned to it  AURORA XMP logic and assumptions are used to simulate when thermal outages occur

7. Northwest Transmission Outages Transmission Link Percent of Time at Full Capacity Percent Time between zero and full capacity Percent Chance of 100% outage Montana to Northwest 2,200 to NW; 1,350 to MT 85%14.9%0.01% BC to Northwest 3,150 to NW; 2,000 to BC 85%14.9%0.01% So. Idaho to Northwest 2,400 to NW; 1,200 to S. Idaho 85%14.9% 0.01% N. Nevada to Northwest 300 to NW; 300 to N. Nevada 85%14.9%0.01% COI 3,675 to NW; 4,136 to N. Cal (seasonal) 85%14.9%0.01% PCDI 3,100 to NW; 3,100 to S. Cal (seasonal) 99%0.5%  Transmission paths that are directly connected to the Northwest are assigned an availability factor  These availabilities are not based on any historical or predicted outages and should be refined

8. Energy Exports- Jan aMW  4,538 aMW are exported from the region  British Columbia and S. California are a majority importing areas  Few hours where there are no regional exports

9. Energy Imports - Jan aMW  1,781 aMW are imported to the region  Most of importing energy comes from Wyoming (Jim Bridger Plant)  Montana imports are shown on the next slide

10. Internal Trading  Chart shows to & from area exchanges between the three northwest areas  Major exchange is from Montana to the Pacific Northwest

11. LOLP Results  5 Iterations had a loss of load; 0.25% of 2,000 iterations (1 in 400 Years)  103 hours had loss of load; 0.015% of 672,000 hours studied Worst Hour of Five Load Loss Iterations Analysis

12. Next Steps  Receive feedback from Technical Committee  More accurately model transmission outages and increase the quantity of lines with outages  Record more outputs on hourly basis  Add internal transmission paths to the Northwest  Evaluate available imports from other regions  Benchmark results to other models