Industry News

What is the common mode and differential mode surge protection of surge arrester?

Differential mode surge refers to the surge applied between the live line L and the zero line n at the input end of the power supply system, or between the lines of the three-phase power supply line. The huge voltage difference will cause damage to the electrical equipment. In case of differential mode failure, the electrical equipment fails, and the protection circuit and surge lightning protection device (varistor) have obvious scorch marks.

Common mode surge refers to the surge applied between L / N and ground PE at the input end of the power line. Theoretically, if there is differential mode surge, there must be common mode surge. When the common mode protection fails, it is shown that the electrical equipment is broken down and damaged to the ground, but the input L / N protection circuit and surge lightning protection device (varistor) are intact. Generally, this kind of situation occurs only when the shell of outdoor electrical equipment is struck by lightning. Such faults can be reduced by good grounding measures.

The grounding is good. When a large common mode surge comes in, huge energy can be quickly discharged to the ground through the common mode circuit or shell, which will not cause fatal damage to electrical equipment; If there is no reliable grounding, even if the common mode circuit is set, it has no obvious effect. The huge surge can only be discharged to the power end through the circuit circuit circuit in the electrical equipment, while the withstand voltage of the insulating layer is limited (below 2500V), and the withstand voltage is far lower than the peak voltage of the large surge, which will cause the insulation breakdown of the electrical equipment to the ground.

In addition, grounding is also an important safety measure! If not grounded, in case of insulation failure, the shell is charged, which is easy to cause electric shock! Generally, formal installation requires that special grounding piles be set nearby, and the electrical equipment shall be reliably grounded. At least the electrical equipment shell or LED lamp installation rod shall be reliably grounded.