2009 Scenario Reliability Assessment - NERC

Regional Reliability Scenario Self-AssessmentsDeveloping a dynamic scheduling system consisting of standard protocols andcommunication infrastructure that would allow access to resources across multipleBalancing Authorities, subject only to transmission constraints. 115Potential Operational Issues Lessons-LearnedOperational issues vary significantly depending on the size of the BA, the mix of generation,penetration of wind, geographic dispersion of wind, market structure, and performance of windplants. There are many and varied methods to mitigate the reliability and operational impacts ofvariable generation. However, these methods all focus on reducing the uncertainty of variablegeneration and accessing flexibility in the existing generation. This can be accomplishedthrough: Larger balancing areas (actual or virtual) Better wind forecastingGeographically dispersing wind generation over a larger areaIncreasing the amount of flexible generation (ramping capability, increased regulationrequirements, decreasing minimum points for fossil power plants, increased need for faststart from cold conditions for fossil power plants)Ability to access flexible generation, including bi-lateral agreements between utilities ormarketsRules and technology that allow for operational flexibility in near real-time throughdynamic scheduling, intra-hour re-dispatch, and ancillary service marketsOperational Limits and ConditionsAt high levels of variable generation — specifically wind — it is possible that ramp controls orgeneration caps may be necessary. The extent to which ramp or other operational limits arenecessary would depend in large part on the other mitigation methods detailed above,transmission system additions, and the future technologies that enable more flexibility in theload.Reliability Assessment AnalysisWECC constructed this scenario to meet the required study goals and it is not directlycomparable to the Long-Term Reliability Assessment case. Renewable resources were distributedacross WECC based on areas of high resource potential, as consistent with existing Western RPSrequirements. However, no attempt was made to simulate the assignment of any particularresource or set of resources to any particular LSE or Region. Using a different set of assumptionsthe results could be, and should be, vastly different.Given that the Long-Term Reliability Assessment is based on utility-submitted resources and thescenario is designed to meet resource adequacy margin targets, the meaning and value of acomparison of this type is not clear. The differences are entirely a function of the study processand not of any inherent characteristics of the resources involved or of utility plans.WECC does not currently do LOLE, EUE, etc., studies. It assesses resource adequacy againsttarget reserve margins.115 http://www.columbiagrid.org/ji-nttg-wc-overview.cfm2009 Scenario Reliability Assessment Page 173