A surge arrester, also known as a surge protector or lightning arrester, is a device used to protect electrical and electronic equipment from voltage spikes or surges caused by transient events such as lightning strikes, power grid switching, or sudden electrical load changes. These voltage surges can potentially damage or destroy sensitive electronics by exceeding their designed operating voltage.
Surge arresters work by diverting excess voltage away from the protected equipment and safely dissipating it to the ground. There are two main types of surge arresters: voltage switching type and current limiting type.
Voltage Switching Type:
This type of surge arrester uses a spark gap mechanism to redirect the high voltage surge to the ground. The spark gap is a small gap between two conductive electrodes that does not conduct electricity under normal operating conditions. When a voltage surge exceeds a certain threshold, the gap ionizes and allows current to flow through it, creating a low-resistance path to the ground. This effectively shunts the excess voltage away from the connected equipment. Once the surge passes, the spark gap returns to its non-conductive state.
Current Limiting Type:
These surge arresters use metal oxide varistors (MOVs) or silicon avalanche diodes to limit the amount of current that reaches the protected equipment during a surge. These components have nonlinear voltage-current characteristics, meaning their resistance decreases as voltage increases. When a surge occurs, these components start to conduct, effectively absorbing the excess energy and limiting the voltage that reaches downstream equipment. Once the surge subsides, the resistance of the components returns to its high state.
Modern surge arresters often combine both voltage switching and current limiting technologies to provide comprehensive protection against a wide range of surge events. They are typically installed at the point where electrical power enters a building or at critical points within the electrical system, such as near sensitive electronic equipment.
It's important to note that while surge arresters can provide effective protection against many surge events, they might not be able to fully protect against extremely high-energy events like a direct lightning strike. In such cases, additional measures like lightning rods and proper grounding systems might be necessary to minimize the risk of damage.