Common Lightning Protection Devices

Lightning protection device is used to reduce material damage and casualties caused by lightning strikes, and it is an important aspect of safety production measures. The comprehensive and systematic installation of lighting protection devices can effectively reduce the potential lightning hazards. So what are the components of lightning protection devices?

Lightning is a natural disaster, which strike voltage is very high. It will not only cause damage to equipment or facilities, cause large-scale power outage, but also cause fire or explosion, and even endanger personal safety. The effective measures to prevent direct lightning strike are lightning rod, lightning wire, lightning belt and lightning arrester.

The Lightning Receptor

The lightning receptor, including the lightning rod, the lightning belt and the lightning net, is an effective measure for preventing direct lightning strikes. The function of the lightning receptor is to lead the lightning to itself, through the down conductor connected to it. And the lightning current is discharged to the earth through the earthing devices, such as the earth cables, to protect the electrical equipment, lines and buildings within its range from lightning strikes. Lightning rods can be divided into the independent lightning rods installed separately from the building and the lightning rod attached to the top of the building. Lightning protection belts and lightning protection nets are generally installed around the top of the building to protect the building.

The Lightning Wire

The lightning wire is composed of a horizontal grounding wire suspended in the air, a grounding conductor and an earthing electrode. The distortion of lightning wire to thundercloud electric field is smaller than that of lightning rod, so its lightning absorption and protection width are smaller than the lightning rod, but this can reduce the number of lightning drops. The protection length of the lightning wire is the same length as the electric cable, so it is especially suitable for protecting overhead wires and large buildings. In recent years, most countries in the world have adopted lightning wires to protect large-scale high-voltage substations of 500kV. The influence of sag should be taken into account when determining the height of overhead lightning line. In the case that sag cannot be determined, the sag of midpoint of overhead lightning wire should be 2 m when the distance between contour pillars is less than 120 m, and 3 m when the distance is 120-150 m.

The Lightning Arrester

The lightning arrester is a protective device to prevent the harm caused by the thunder and lightning intrusion wave. When the thunder and lightning intrusion wave intrudes along the line, the lightning protector can guide the lightning current to the earth in time to prevent electrical equipment from being struck by lightning. The lightning arrester is an over-voltage limiting device. In the early stage, it was mainly used to limit the amplitude of lightning over-voltage transmitted from the line, and later developed to limit some small energy switching over-voltage. In recent years, it has been extended to the field of line lightning protection and deep limit switching over-voltage, so it can also be called voltage limiter. When the voltage limiter is used, it is installed near the protected equipment and connected between the phase line of the protected equipment and the ground. 

Normally, when the voltage used on the voltage limiter is the relative ground voltage of the grounding system, the voltage limiter is not conductive (leakage current flowing through the micro-ampere level at most). In the case of over-voltage, when the voltage used on the voltage limiter reaches the action voltage of the voltage limiter, the voltage limiter conducts, releases the over-voltage energy through high current, and limits the over-voltage to the allowable level, so as to achieve the purpose of protecting the equipment. After the release of over-voltage energy, the voltage limiter should be able to automatically restore to the non-conducting state, so that the system can resume normal operation. Over-voltage limiters used in power systems include protection clearance, exhaust arrester (tube arrester) and valve arrester, among which valve arrester is the most widely used.

In summary, the lightning rods are mainly used to protect open-air power generation, power distribution units and buildings. The lightning wires are most suitable for long protections such as power lines. Lightning protection nets and lightning protection strip are mainly used to protect buildings. The lightning arrester is used to protect electrical equipment.