Accommodating High Levels of Variable Generation - NERC

Transmission Planning & Resource Adequacy
obstacles, accelerate siting, and approve permits for transmission infrastructure construction and
upgrades. Customer education and outreach programs should be fostered to improve the public’s
understanding of the critical need for transmission, the issues and trade-offs, its role in
supporting the overall reliability of the bulk power system, and the need for new transmission
infrastructure to support variable generation (renewable) resources. The task force recommends:
Industry Action: State, provincial and federal agencies and policy makers should consider:
o The impacts of variable generation integration on interstate and provincial bulk
power system reliability in their oversight and evaluations.
o Collaborative efforts needed to remove obstacles, accelerate siting, and approve
permits for transmission line construction.
o The importance of coordinated transmission and resource planning.
o The issues and opportunities associated with larger balancing areas and the
desirability of shorter resource scheduling intervals or regional dispatch
optimization.
3.2. Resource Adequacy Planning
The overarching goal of resource planning is to ensure that sufficient resources, delivery
capacity, and reliability characteristics exist to meet future demand requirements in a reliable and
economic manner. All resource planners maintain some percentage reserve margin of capacity
above their demand requirements to maintain reliability following unexpected system conditions
and to meet state regulatory and regional requirements. Reserve margins are determined by
calculating the capacity of supply resources, discounted to reflect the potential unavailability of
the resource at high risk times.
In high variable generation penetration scenarios, a larger portion of the total supply resource
portfolio will be comprised of energy-limited resources when compared to today’s power
system. This fact somewhat complicates, but does not fundamentally change existing resource
adequacy planning processes in that the process must still be driven by a reliability-based set of
metrics. The analytical processes used by resource planners range from relatively simple
calculations of planning reserve margins to rigorous reliability simulations that calculate system
Loss of Load Expectation (LOLE) or Loss of Load Probability (LOLP) values. 50 In the latter
case, planners then periodically confirm resource adequacy indicated by the calculated reserve
50 A traditional planning criterion used by some resource planners or demand-serving entities (LSEs) is maintaining
system LOLE below one day in ten years.
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