Most of us are aware of the wildfires in California, which have become increasingly regular and severe. The devastating and unfortunate impact on families and communities deserves the most attention and support, but I’d like to raise a more subtle but consequential ripple effect of the fires on the electric power industry. And no, I’m not talking about PG&E being brought to the brink of bankruptcy. I’m talking about the grid events of the Blue Cut wildfire that is having a dramatic and defining impact on the future of renewable generation like wind and solar on the US grid.
In August 2016, the Blue Cut wildfire was burning through land and property in southern California. At the same time that gigawatts of solar PV in the region were generating electricity, the fire was generating smoke headed for major transmission line corridors. Smoke degrades the insulating properties of air, and this caused a temporary fault on one of the major transmission lines. The fault was detected and cleared as designed -- within 50 milliseconds. The grid self-protected and carried on without a hiccup, or so it initially seemed.
It soon became clear through careful analysis of SCE that nearly 1,200MW of solar generation tripped offline at the instant of the fault, causing a massive generation deficit on the Western Interconnect that was visible from Arizona to Alberta. While the system recovered from the deficit in several seconds, leaving no one in the dark, the warning shot was heard loud and clear by NERC, FERC, and dozens of industry stakeholders. It was clear that a larger event of the same nature could have resulted in a widespread blackout. The teams jumped in to understand the cause of destabilizing behavior observed and how to correct it before the next event created new headlines.
The root cause for so much solar generation tripping offline -- at a time when the grid needed the support the most -- lies deep within the firmware of the solar PV inverters. All inverters contain many self-protecting functions that are capable of taking the unit offline in a fraction of a second at the sign of trouble. But the distinction between “trouble” for the inverter and an “all-hands-on-deck” grid emergency is critical to system reliability. The challenge for equipment manufacturers is that this distinction must be spot-on every time and performed faster than the self-protection functions.
Recognizing this and many other ambiguities about the performance of inverter-based resources (solar, most wind, battery storage), NERC assembled an industry task force to codify performance in a comprehensive guideline. Last week, it held the first workshop to get the word out to system operators and other stakeholders. Now, th
e principles from the guideline are permeating the industry and evolving into a standard. The quick response, with NERC’s leadership, is helping the industry navigate unforeseen challenges on the way to increasing shares of renewable generation, which is dominated by inverter technology.