Researchers at the National Renewable Energy Laboratory (NREL) have learned a lot about how to reliably integrate large amounts of wind and solar power onto the grid—but there are a few outstanding challenges. One such challenge is making sure the grid is protected if there is a fault, such as a short circuit. In a new guidebook and explainer video, NREL explains how to solve this challenge and maintain power systems protection with higher levels of renewables in the future grid.

The Next Challenge To Tackle After Inertia

In the electric power sector, there has been considerable effort to understand how grid planning and operation might change with large-scale deployment of resources like wind and solar photovoltaics (PV), which use inverters instead of the synchronous generators in conventional power plants.

The associated decline in power system inertia had been thought to pose a major challenge to maintaining a reliable future power system. In 2020, NREL countered this by releasing a video and guide explaining the role of power system inertia in keeping the lights on.

These pieces described how although growth in inverter-based resources will reduce the amount of inertia on the grid, there are multiple existing or possible solutions for maintaining or even improving system reliability—so grid planners and operators have no need to panic.

However, inertia is just one of several challenges that need to be addressed as the grid evolves.

“While it hasn’t been discussed as widely as inertia, fault protection is another issue to figure out as inverter-based generation continues to grow,” said Paul Denholm, NREL principal energy analyst and lead author of both guides. “And we have ideas on how it can be addressed.”

What Is Fault Protection and Why Does It Matter?

The most typical type of 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. This is called fault current, and it can lead to fires and damage equipment if not corrected.

In today’s power system, fault current is mostly produced by synchronous generators in fossil, nuclear, and hydroelectric plants, which can inherently produce large amounts of current. However, inverter technology is not typically designed to produce large amounts of fault current—so in a future grid with high levels of solar PV and wind, the power system may need to find new ways to provide fault protection.

Source: NREL