The Western Electricity Coordinating Council (WECC) on Sept. 20 issued the “2011 State of the Interconnection” report, the first of what will be annual reports that evaluate risks to system reliability by analyzing events, real-time performance measures, compliance violations, and planning observations across the Western Interconnection.
The 2011 report will serve as a baseline for all future state of the interconnection reports, WECC CEO Mark Maher said in a statement accompanying the report.
WECC staff already provides its reliability policy issues committee (RPIC) with periodic updates on the areas addressed in the report for its use in evaluating risks to system reliability. The annual report was developed and designed to provide those same topical updates, but at the annual-level scale and to a larger audience, Maher said.
The 29-page report addressed system outages, compliance violations, system performance including frequency and voltage data, and planning including adequacy and planning margins. It also made recommendations in each area.
In the report, WECC said outage rates in the Western Interconnection remained relatively unchanged throughout 2011 when compared to the average range for the previous three years. During 2011, there were 93 reportable events where NERC brief reports were submitted, including 66 Category 1 events, 25 Category 2 events, one Category 3 event, and one Category 4 outage. Outages can be rated as severe as a Category 5.
Two major exceptions were noted: a weather-related outage in the El Paso Electric (EPE) service territory on Feb. 1-5, and the string of more than 30 outages that struck Arizona, southern California, and Baja California on Sept. 8.
During the EPE event, sustained record low temperatures coupled with severe winds caused the loss of “a significant amount of local generation, impacting EPE’s load serving capability,” WECC said in the report. As a result, the utility experienced four separate instances of controlled shedding of firm load, affecting approximately 100,000 customers.
“This preemptive action effectively prevented a blackout of the EPE system as well as any failures that could have cascaded into the Interconnection,” according to the report. No transmission was affected during the Category 2 event.
The Sept. 8 event was the string of outages that affected portions of Arizona, southern California and northern Baja California during the 11 minutes following the loss the Hassayampa-N. Gila 500-kV line in Arizona Public Service (APS) territory. The loss of the line triggered a system disturbance that lead to cascading outages and the loss of more than 7,000 MW of firm load, leaving about 2.7 million customers without power, some for up to 12 hours, according to the May 1 FERC/NERC report on the Category 4 outage.
“Despite these major events, the outage rates remained within the average range for the three-year period evaluated,” WECC said.
During 2011, there were 93 reportable events where NERC brief reports were submitted. An event analysis was prepared for eight of those events. Of these 93 events, 66 were classified Category 1, 25 were Category 2, one was Category 3, and one was Category 4.
Compliance violations low
For 2011, there was no readily apparent correlation between standards violation trends and transmission outage rates, WECC said in the report.
Standards requirements violations were relatively stable during 2011, but the report noted the number of standards requirement violations with severe or moderate impact on reliability have trended down over the last four years and in 2011 was significantly lower than in 2008. That reduction in the number of severe or moderate violations continues a four-year downward trend, according to the report.
One exception was the area of critical infrastructure protection (CIP) compliance. During 2011, there were 579 CIP violations, including 13 “severe” violations. However, the report noted that “CIP requirements are relatively new” and that the relatively high number of CIP violations “reflects a ‘start-up’ compliance condition.”
System performance and planning
The power supply for the Western Interconnection in 2011 met the need for actual demand, with a reserve margin of 28.2% for summer and 34.8% for winter. The summer peak load for the Interconnection was 152,211 MW and 131,471 MW for the winter peak.
WECC said in the report that it is important to note that some parts of the Western Interconnection are summer peaking, while others are winter peaking.
Variations in frequency and voltage across the system were “largely unremarkable and exhibit[ed] expected variability,” with only a few exceptions, the report noted.
During 2011, 6,158 MW of generation capacity was installed in the Western Interconnection. That included 95 MW of biomass, 835 MW of coal-fired generation, 1929.8 MW of gas-fired gen, 129.5 MW of geothermal, 3.0 MW of hydro, 208.8 MW of solar, and 2957.6 MW wind. When unit retirements were accounted for, 2011 saw an increase in generation maximum capacity of 5,666.5 MW.
The report noted that wind made up nearly half of the total installed capacity, and noted that nonconventional generation installations for wind are increasing annually. “As variable generation penetration increases within the Interconnection, this will present additional challenges to reliability,” WECC said in the report.
WECC recommended several actions in the report’s outage category. Those include a concentrated effort to gather more meaningful results from common rights-of-way and tower-line outage data to look at how physical attributes influence line performance. Recommendations also include further refining the event severity index, and the weighting of load and generation loss and the effect of the event on transmission availability. Finally, the report said prompt correction of identified causes, support for developing industry lessons learned, and performing a detailed compliance self assessment should be continually monitored and improved on.
Future reports should drill down more deeply into the root causes of compliance violations, according to the report. That deeper look will help “determine whether there are lessons or recommendations for outreach, education, and training on requirements that may be most problematic,” WECC said in the report.
Recommendations on system performance were the briefest of the report’s four focus areas, and called for more consistent voltage control across buses.
Planning could be improved by supplementing the margin analysis currently performed “with additional probabilistic studies that will indicate loss of load expectations and potential unserved energy,” WECC said.
WECC will host an informational webinar to discuss high-level observations of the report as well as next steps on Sept. 27.