European products are generally labeled with the maximum discharge current, and the product model is also set based on this parameter. For example, a well-known European brand XXX65 and XXX40, where the values of 65 and 40 are Imax. However, Chinese standards clearly stipulate that the nominal discharge current In should be used for selection, which is an awkward situation encountered in engineering design at present. After checking the product information, the In value of XX65 does not exceed 20kA, and the In value of XX40 does not exceed 15kA. If the recommended values of GB50343 are followed, these two products can only be used for three-level protection at the end of the equipment. However, in actual design, they are installed on the first and second levels, which is clearly inconsistent with the selection parameters of national standards, and the residual voltage is high. Ordinary models generally exceed 1200V. Once the wiring environment is not good, it is easy to exceed the equipment's withstand voltage value. Generally, European products have a relatively small Uc value and are opportunistic in labeling line voltage, making it easier to mislead when selecting models.

The surge protector is suitable for the protection of 220/380V low-voltage power supply and is a nonlinear component. According to IEC standards, the surge protector is a device mainly used to suppress the overvoltage and overcurrent of the transmission line. The basic requirement for a surge protector to play a protective role is to withstand the expected lightning current and effectively extinguish the power frequency continuous current generated after the lightning flow through the maximum clamping voltage of the surge. It limits the instantaneous overvoltage that enters the power line or signal transmission line to the voltage range that the equipment or system can withstand, or discharges strong lightning current into the ground to protect the protected equipment or system from damage caused by impact.

The surge protector MOV consists of three parts: a metal oxide material in the middle, connected by two semiconductors to the power supply and ground wire. When a surge occurs, the MOV immediately acts with a response time of 1-3 nanoseconds. The "V" in MOV is a rheostat. At the moment of response, the resistance of the MOV drops from its maximum value to almost zero ohms, and overcurrent flows into the ground through the MOV. The protected electrical equipment continues to operate at normal operating voltage. Its semiconductor components have the property of changing resistance with voltage changes. When the voltage drops below a specific value, the movement of electrons in a semiconductor generates high resistance. On the contrary, when the voltage exceeds this specific value, the motion of electrons will change, and the semiconductor resistance will decrease to nearly zero ohms. The voltage is normal, and the surge protector MOV is idle on the side, without affecting the power line.