USF Path 66 Analysis Update January 31, 2013 Robin Chung UFAS Chair

Background In 2012, WECC experienced significant utilization of the Unscheduled Flow Mitigation Plan (UFMP) From 2011 to 2012, Plan usage increased significantly The majority (~90%) of this increase was on Path 66, the California-Oregon Intertie UFAS tasked with determining cause(s) of this increase

Path 66 Hours of Coordinated Operation of Phase Shifters –2010 : 200 hours –2011: 322 hours –2012: 2513 hours Hours of Curtailments –2010 : 59 –2011: 55 –2012: 1112

Path 66 Relief MWh of Relief by Curtailment of Off-Path Schedules: –2010 : 8,059 –2011: 8,634 –2012: 138,139

For All Qualified Paths Hours of Coordinated Operation of Phase Shifters –2010 : 446 hours –2011: 714 hours –2012: 2787 hours Hours of Curtailments –2010 : 132 –2011: 206 –2012: 1300

Potential Contributing Causes Degree of on-Path Utilization Effectiveness of Qualified Controllable Devices (Phase Shifters) Appropriateness of Initiation and Termination of UFMP Events Interconnection-Wide Generation Dispatch Patterns Effect of Reliability- Based Control Field Trial (RBC)

Degree of Path Utilization From 2010 to 2012, Path 66 utilization has significantly increased Measured as percentage of on-Path schedules versus Path Limit (SOL) Usage is expected and entirely allowable; Path owners have a right to utilize their capacity

Path Increased Utilization Factors Path 66 SOL generally lower in 2012 compared to previous years –Significant restrictions for many hours (below 2800 MW SOL), including outage resulting in 600 MW SOL Path 66 on-Path scheduled energy was higher

Impact of Increased Path Utilization Less margin to absorb unscheduled flow: USF has a higher impact when SOL is reduced Observed that for most months in which on- Path schedules exceeded 65% of Path SOL, UFMP usage increased Conclusion: Path utilization deemed to be a large contributor to the 2012 USF increase

Phase Shifter Effectiveness Significant PST outages for 9 out of 12 months in 2012 Measure PST effectiveness by looking at COPS hours to contributing schedule curtailments Ratio of COPS/Curtailments in 2012 the lowest ratio in past 11 years –2010: 3.4 –2011: 3.5 –2012: 2.1

Phase Shifter Effectiveness One particular Qualified Device outage is believed to cause between MW of impairment to Path 66 USF relief Resulted in an additional MWh of off- Path curtailments during each hour of curtailment events Conclusion: Phase Shifter Effectiveness is deemed to be a large contributor to the 2012 USF increase

Appropriateness of Event Initiation and Termination Data in webSAS tool suggests some events did not meet the 95% Path loading threshold and that certain events were not terminated when they dropped below the 92% threshold UFAS review of details and circumstances around these events found they were generally in accordance with Plan documents

Explanation of webSAS Data Indicators Path Operator utilized alternate mitigation actions (circulation on the DC Intertie, independent use of PSTs) Indication that termination of event would result in immediate recurrence of USF problem Conclusion: Event Initiation and Termination is deemed to be a small/negligible contributor to the 2012 USF increase

Interconnection-Wide Generation Dispatch Patterns Large Generation outage (SONGS) of 2300 MW in CISO BA Good water year in Pacific NW Compared Net Scheduled Interchange (NSI) for 2 day period in March 2012 to comparable 2 day load period in March 2010

NSI Statistics Higher exports from BAs North of Path 66, particularly BPA Higher imports South of Path 66, particularly CAISO and LAWP Additional examination necessary to confirm this finding Conclusion: Generation Dispatch Patterns are deemed to be a medium contributor to the 2012 USF increase

Effect of Reliability-Based Field Trial (RBC) Several approaches examined by UFAS and other observers Conflicting conclusions exist based on available information and study Four different approaches taken

Minute-by-Minute ACE Analysis for 30 USF Events from 2012 Data consisted of BA ACE for each minute of a two- hour span of 30 events BAs organized into three geographic/electric regions –North of P66 –South of P66 –East of P66 Less than 10% of the minutes of the 30 events exhibited positive ACE in north bubble coincident with negative ACE in the south bubble. When effect of East group is considered, 39% of the minutes exhibit some exacerbating contribution of BA ACE to Path 66 USF

Powerex Analysis for 30 USF Events from 2012 Powerex used same 30-event data, assumed ACE is correlated and causatory Concluded that up to 47% impact on magnitude of USF energy/curtailments. Concludes that the degree of curtailment was worse under the period of RBC field trial

WSM Power Flow Analysis for 30 USF Events from 2012 WECC Staff conducted analysis using power flow adjustments to correct BAs found to be outside their L10 limits back to L10 Simulated the effects of operation without the RBC Field Trial; i.e. under the prior CPS2 limits In four cases, correction to the L10 would have increased the Path 66 USF (RBC was benefitting) In all but one of the remaining cases, correction to L10 would have provided an average of 2% reduction in path loading In one case, this correction to L10 exhibited a 19% decrease in path loading (SOL of Path MW) Analysis indicated that the RBC field trial had little effect on the number of USF events for Path 66

Detail Examination of March 28, 2012 Path 66 Event The data includes minutes prior to event initiation, while Path Operator making a determination about initiation UFMP. North of Path 66 BA group was only in excess of group ACE L10 for one minute; South group aggregate ACE was always within the group ACE L10 limit Indication that the RBC Field Trial operation was not contributing to the Path 66 USF for this event However, if we isolate BAs immediately adjacent to Path 66 (PACW, BPA north of Path 66 and CAISO, BANC, LDWP south of Path 66) there does seem to be an exacerbation of southbound flow on P66. Additional analysis needs to be done to determine impact of ACE of immediately adjacent BAs to the Qualified Path.

Other Observations related to RBC L10 limit went to 100 X L10 in April, 2011, and from that date forward P66 USF was lower than all previous months. There is no statistical correlation between ACE of the North and South BAs and the amount of USF appearing on Path 66 Relatively large ACE values, if aligned in a pattern with high positive ACE north of the Path 66 and high negative ACE south of the Path, will exacerbate the amount of USF on Path 66; Most of the ACE levels analyzed, however, would have been allowed under the prior BAL-001 Standard, and CPS2 performance would have been satisfactory.

Other Observations Related to RBC, Continued Path 66 Unscheduled flow annual energy totals have actually declined from 2010 to 2012

Conclusions and Recommendations to Date 1.Degree of Utilization of Path 66 was a large contributor to the increase of Path 66 USF events 2.Significant outages of several Qualified Devices eroded the effectiveness of the PST element of the Plan and drove much higher degrees of off-Path contributing schedule curtailments 3.While some instances of inappropriate execution of the UFMP occurred, this had little impact on the observed increase in Path 66 USF events 4.The Interconnection experienced considerable change in generation dispatch patterns, resulting in higher exports from the Pacific Northwest, and higher imports to California. UFAS categorizes this as a medium contributor to the increase of USF events on Path 66. Additional examination would be necessary to confirm this finding

5.The examination of the effects that the Reliability-Based Control Field Trial (RBC) had upon the Path 66 USF statistics is only preliminary at this time, yet the majority of the facts suggest that RBC is a small contributor to the 2012 Path 66 USF events. –Additional study is necessary to make a definitive conclusion –To pursue this analysis, study engineering resources would be necessary –No recommendation is warranted at this time for alteration of the RBC Field Trial based on UFAS examination of the facts

UFAS Recommendations UFAS should investigate the possibility of accelerating the return to service of key Qualified Devices under the UFMP Additional study engineering resources are necessary in order to make a definitive conclusion about the impacts of the RBC Field Trial on Path 66 USF statistics Analyses similar to that which was conducted for Path 66 is warranted for other Qualified Paths No adjustment or alteration to the RBC Field Trial is warranted at this time; however, the RC is encouraged to continue to assess ACE levels of key BAs when considering initiation or termination of UFMP steps