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Varistor and lightning protection resistance

time:2021/3/20   source:华天电力  reading:591 time

The lightning protection standard resistance is used for the calibration of grounding resistance testers, equipotential testers and other instruments. The grounding resistance of the lightning protection device refers to the grounding resistance value of the lightning protection device's ground resistance of the first, second and third types of lightning protection buildings. There is nothing else to refer to. The national standard stipulates that the grounding resistance of each downconductor of Class I and Class II lightning protection buildings shall be ≤10 ohms, and the requirements of Class III buildings shall be ≤30 ohms. Electrical lightning protection is a systematic project, which is generally divided into internal electrical lightning protection devices and external electrical lightning protection devices. The two are mutually indispensable.

Lightening Protection Components Tester.png

External electrical lightning protection devices are set up to protect buildings, substation and distribution equipment, power lines, etc. from fire accidents and personal safety accidents caused by lightning strikes. Commonly used are lightning rods, lightning protection wires, lightning protection nets, lightning protection belts, lightning arresters, etc. Types, different types of external electrical lightning protection devices have different protection objects. Lightning rods are mainly used to protect buildings, structures and power distribution equipment; lightning lines are mainly used to protect power lines; lightning nets and lightning belts are mainly used to protect buildings; lightning arresters are mainly used to protect power equipment.

Varistor is one of the most used voltage-limiting devices. Varistors include silicon carbide varistors and zinc oxide varistors. Commonly used is zinc oxide varistor, which is mainly based on zinc oxide as a raw material, adding a variety of trace metal oxides, mixed molding, sintering and assembly to form an overvoltage protection device. The outer cover is epoxy resin.

Varistor current capacity: After a specified waveform current is applied to the varistor at a specified time interval and number of times, the maximum current amplitude that can pass through the reference voltage of the varistor is still within the specified range.

In practical applications, the surge current absorbed by the varistor should be less than the maximum peak current of the varistor to extend the service life of the product. Different use occasions, the purpose of applying varistor, the voltage/current stress acting on the varistor is not the same, so the requirements for the varistor are also different, pay attention to distinguish this difference, it is very important for correct use of. According to different purposes of use, varistors can be divided into two categories: varistors for protection and varistors for circuit functions.

The difference between a varistor and a lightning protection standard resistor is one for overvoltage protection and the other for lightning protection. The current capacity is different, the difference is more than 10 times, the latter can absorb more surge current.

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