What does a counterpoise connect in a lightning protection system?

In a lightning protection system, a counterpoise serves as a grounding component that connects all down conductors at or below grade. It is designed to provide a common grounding point, which improves the overall safety and effectiveness of the lightning protection system by ensuring that there is a low-resistance path to ground for lightning currents.

The counterpoise typically consists of a network of conductors buried in the ground, which helps to spread the lightning strike current over a larger area, thereby reducing the potential for damage. Connecting all down conductors through the counterpoise allows for a unified grounding system, helping to prevent back-feeding of energy and ensuring that any electrical surges are safely dissipated into the earth.

This setup enhances the overall performance of the lightning protection system and minimizes the risk of electrical hazards. The other answer options involve different components or functions of a lightning protection system but do not specifically relate to the main role of the counterpoise in connecting down conductors to ground.