Power System Protection

NREL is researching how to maintain power system protection on the evolving power grid.

Growing deployment of inverter-based resources such as wind, solar photovoltaics (PV), and battery energy storage has raised questions about how to protect the power grid if there is a fault, or abnormally high or low electrical current, which can happen for a variety of reasons. NREL has researched how to solve this challenge and maintain power system protection with higher levels of renewables in the future grid.

Fault Protection and Why It Matters

The most typical type of grid fault is a short circuit. On the power grid, short circuits can occur, for example, when two wires touch, or when a tree touches a wire. This causes the generators to produce a big surge of electrical current, also known as fault current. The surge can lead to fires and damage to equipment, if not corrected.

Fault current can also be helpful, though, because it alerts the grid that something isn't right. Circuit breakers on the grid detect the abnormally high levels of current and disconnect that part of the grid, which prevents damage, which must happen quickly.

Maintaining Fault Protection on the Evolving Power Grid

In today's power system, fault current is mostly produced by synchronous generators in fossil, nuclear, and hydroelectric plants that can inherently and automatically produce large amounts of current.  Many of these traditional generators are being replaced with inverter-based resources, which are not typically designed to produce large amounts of fault current like traditional synchronous generators.

There are multiple options to maintain fault protection with high levels of inverter-based renewables that are already being used in locations throughout the United States. One option is to deploy inverter-based resources that have the ability to provide more fault current (requiring oversizing certain components in the inverter). Another option is to rely on synchronous generators. These include renewable resources that use synchronous generators (such as concentrating solar power, biomass, or geothermal), and deploying stand-alone devices installed to provide fault current.

Additional Resources

To learn more about operational reliability on the evolving power grid, check out these resources:

Understanding Power Systems Protection in the Clean Energy Future

Inertia on the Power Grid Video

Inertia on the Power Grid Fact Sheet

Inertia on the Power Grid Technical Report

Want more renewable energy grid basics? See more topics on planning and operating the future grid.