The summer of 2019 has provided several reminders - blackouts in Argentina, Kauai, UK, and Manhattan - that keeping the electric grid running is an elaborate balancing act that must be kept up every second of every day. We have become so accustomed to reliable electricity that it’s easy for many of us to not realize that behind the scenes, a massive system of systems is in a continuous balancing act.
Consider the grid as a human pyramid - many different people (components) participating in a single effort - each performing his or her own challenging task, and relying on others to do the same. This show must go on through the broiling heat and freezing cold. And without warning, members of the pyramid are shoved from behind (lightning strikes, trees falling on lines) - so hard that some folks will be forced to jump out of the pyramid. But the team - a team of hundreds of thousands - must quickly adjust and continue standing. Should the pyramid collapse, it is expected that there are no broken bones (no permanent equipment damage). And finally, this wild, outlandish, and riveting show must be very affordable for everyone.
Just as the actions taken by individuals in the pyramid must be fast and yet coordinated, so must the grid. In the August 9th outage in the UK, a sudden loss of very large generating plants knocked the system off-balance. As other generators rushed to respond to make up for the shortfall, it was clearly too little and/or too slow to respond, which triggered the emergency load-shedding system and significant customer interruption. The on-going investigations will shed more light on the root causes for the loss of generation, and while it is important to minimize the probability of a generation loss, it will never be zero.
This underscores the importance of the systems that are designed to respond after a loss of generation but before emergency load-shedding is triggered. Conventionally, fossil-fired power plants provided the vast majority of these responsive reserves -- and they still do today. However, the grid is evolving to include more renewable technologies that are displacing fossil-fired plants. One of the side-effects of this transition to renewables is that the grid is changing state faster, leaving less time to respond when a generator trips offline. Because of this trend, it’s increasingly important to have diverse set of fast-responding assets that are able to “catch” the grid before it falls into load-shedding. Renewable technologies have an important role to play here, as do responsive loads, as discussed in my previous blog. These technologies exist, but there is a lot more work to be done on the application and coordination fronts. The combination of coordinated technologies is a powerful and effective mitigation against the unlikely - yet inevitable - unplanned loss of generation, while avoiding costly customer interruptions.