金属氧化物避雷器MOA的核心元件是金属氧化物电阻片（MOR），他的主要成分是氧化锌，约占90%。正常时工作在小电流区，在工作电压下呈现很大的电阻，流过MOA的电流很小，约0.1~0.2mA，可以近似认为是断开的。当系统产生过电压时，比如雷电入侵，在过电压作用下MOA呈现低电阻，对地导通，将过电压泄放，只有很小的残压，这样就可以保护其周围的设备不受过电压的危害。
The core component of MOA is metal oxide resistor (MOR), whose main component is zinc oxide, accounting for about 90%. Normally working in a small current region, under the working voltage shows a large resistance, the current flowing through the MOA is very small, about 0.1 ~ 0.2 mA, can be approximately considered to be disconnected. When the system generates overvoltage, such as lightning intrusion, MOA shows low resistance under overvoltage, conducting to the ground, overvoltage will be released, only a small residual voltage, so that the surrounding equipment can be protected from overvoltage.
避雷器的热稳定：避雷器长期承受运行电压，经过多次过电压冲击放电，性能可能变坏，在工作电压下的电流可能增大，导致发热增加，由于其是负温度特性，温度越高电流越大，恶性循环就可能最终导致MOA因温度过高超过了其散热能力而发生热崩溃现象。
Thermal stability of lightning arresters: the arresters withstand operating voltage for a long time, after repeated overvoltage impulse discharges, performance may deteriorate, the current under operating voltage may increase, resulting in an increase in heating, because of its negative temperature characteristics, the higher the temperature, the greater the current, the vicious cycle may eventually lead to MOA because the temperature is too high to exceed Its heat dissipation capacity is subject to thermal collapse.
MOA的额定电压：是指在承受规定的雷电冲击或操作冲击后仍能耐受10s的最高工频电压有效值而不会发生热崩溃。
MOA rated voltage: refers to the maximum power frequency voltage RMS that can withstand 10 seconds of lightning shock or operation shock without thermal collapse.
MOA的持续运行电压是指允许持续长久地施加在两端的工频电压有效值，一般额定工作电压是持续工作电压的1.25倍。
The continuous operating voltage of MOA is the RMS of the power frequency voltage allowed to be applied at both ends for a long time. The rated operating voltage is generally 1.25 times of the continuous operating voltage.