A distribution arrester—people also call it a surge arrester—is an important protective device. You put it on electrical distribution systems, usually systems that go up to 36kV. Its main job is to protect expensive equipment. Think of transformers, switchgear, and cables—this arrester keeps them safe. It does this by controlling temporary high voltages. Those high voltages come from lightning hits or switching surges.
The arrester works on a simple but helpful rule. When the electrical system has normal voltage, the arrester has very high resistance. It acts almost like an open circuit. But when a dangerous high-voltage surge pops up, things shift. The arrester has a special resistor material—most of the time, it’s metal-oxide varistors (MOVs). This material quickly changes to a state with very low resistance. That low resistance makes a better path to the ground, a path that doesn’t block current much. The big surge current then goes through this path instead of hitting the protected equipment. Once the surge is over, the arrester gets back to its high-resistance state right away. This brings the circuit back to normal. It also keeps the ground separated again.
