Describe the role of a surge arrester in protecting distribution equipment from lightning strikes.

Lightning strikes induce high-voltage surges on distribution lines, which can damage or destroy sensitive equipment like transformers, insulators, and underground cables. A surge arrester is a protective device designed to limit these voltage surges and divert the excess current to ground, thereby protecting the equipment. A surge arrester is connected in parallel with the equipment it is protecting. Under normal operating conditions, the arrester acts as an open circuit, allowing normal voltage to pass through to the equipment. When a lightning surge occurs, the voltage exceeds the arrester's protective level. The arrester then rapidly switches to a low-impedance state, providing a path for the surge current to flow to ground. This limits the voltage across the protected equipment to a safe level, preventing damage. After the surge has passed, the arrester quickly returns to its high-impedance state, resuming normal operation. Surge arresters are typically located near equipment that is particularly vulnerable to lightning strikes, such as transformers, cable terminators, and switchgear. The arrester's protective characteristics, such as its voltage rating and surge current capacity, must be carefully selected to match the characteristics of the protected equipment and the expected lightning surge levels. Proper grounding of the surge arrester is crucial to ensure that the surge current is effectively diverted to ground.