Reliability Issues for the Electric System in a Rapidly Changing World

his discussion will discuss how a small US state (Vermont) has been dealing with a high penetration of renewable resources which have been installed in the last 10 years in the state. Based on current renewable generation levels, the state of Vermont has over 65% of its peak load in installed renewable energy with over 80% of that amount being wind and photovoltaic generation.  Most of this is installed on the distribution system and sub-transmission systems.  This state foreshadows what the country may look like in the coming years.

The discussion will point out how the springtime “duck curve” in Vermont has changed in the last five years and how it changes from a sunny day to an overcast day.  In winter climates, snow days make a large impact on the availability of photovoltaic resources.  In Vermont, it is not usual that at least once per winter that over a 4-5 day period that no generation from solar sources was available due to snow on panels.  This impacts the generation capacity of this technology significantly when it is needed most in the winter when natural gas resources may be constrained in New England.   Data will be shown on what happens to a 20MW solar generation field on a partly cloudy day.

Power system reliability and resiliency have many parts to it and there will be a discussion of generation reliability as well the increasing dependence on electricity as an energy source and implications if transmission and distribution systems are not hardened.  Vermont publishes a Long Term Transmission Plan every 3 years.  In the 2021 plan, there are forecasts for both transportation and heating electrification which will be shown.

FERC publishes priorities and risks to the power system every two years.  There are risks identified in four key functional areas.  They are Grid Transformation, Extreme  Natural Events, Critical Infrastructure Interdependencies, and Security  Risks.  Each will be touched upon.

In summary, the power system is changing rapidly along with increasing customer expectations.  This combination increases the risk of large-scale disruptions and engineering solutions may be lagging the new operating parameters which are becoming a reality.