A surge protector (SPD), also known as a surge protector, is a critical device used to protect electrical and electronic equipment from transient overvoltages (such as surges caused by lightning strikes or power grid fluctuations). Its core function is to limit the amplitude of abnormal voltages and safely discharge excessive currents to the ground, thereby ensuring the safe operation of downstream equipment.
The operating principle of a SPD is based on two major mechanisms: voltage clamping and energy diversion. When the normal operating voltage of the power grid is present, the SPD exhibits a high impedance state, barely affecting normal circuit operation. However, once a transient overvoltage (such as a surge caused by lightning induction or switching operation) is detected, the nonlinear components within the SPD (such as metal oxide varistors (MOVs), gas discharge tubes (GDTs), or transient voltage suppressor (TVS)) rapidly respond, sharply reducing their impedance and clamping the overvoltage to a safe range (usually the rated voltage of the equipment). Specifically, metal oxide varistors (MOVs) are the most common lightning protection components. Their characteristic is that they exhibit high impedance when the voltage is below the nominal value. When the voltage exceeds a threshold, their resistance drops sharply, allowing large currents to flow, thereby dissipating the surge energy to ground. Gas discharge tubes (GDTs) are suitable for higher-energy surge protection. When the voltage reaches a certain level, the gas within them ionizes to form a conductive path. Once conducting, the impedance is extremely low, allowing the overcurrent to be quickly diverted. Transient suppressor diodes (TVSs) are commonly used to protect precision electronic equipment. They have extremely fast response times (nanoseconds) and can effectively suppress high-frequency transient interference.
Modern lightning arresters typically employ a multi-stage protection design, combining the advantages of different components. For example, GDTs are used at the front end for coarse protection, while MOVs or TVSs are used at the back end for fine-tuning. This ensures effective protection against surges of varying energy levels. Furthermore, high-quality lightning arresters feature status indicators and failure protection, prompting users to replace protective components when they age or become damaged, preventing protection failure. In short, lightning arresters limit dangerous surge voltages to a safe range through rapid response and energy diversion, and are important protective devices for ensuring the stable operation of power systems, communication facilities, and household appliances.
