Why does lighting hit the lighting arrester ?

Lightning strikes a lightning arrester (or surge arrester) because of its design and purpose in electrical systems. Lightning arresters are installed on structures to protect them from lightning strikes by providing a low-impedance path to ground for the lightning’s electrical energy. Lightning tends to strike the highest point or the path of least resistance to the ground. When lightning approaches a structure, the lightning arrester’s design and placement aim to attract and safely conduct the electrical current from the lightning strike to the ground, thereby preventing damage to the building or equipment connected to the arrester.

Contrary to common misconception, lightning arresters do not attract lightning. Instead, their purpose is to provide a preferred path for the lightning strike to safely dissipate the electrical energy into the ground. Lightning typically strikes structures or objects that are tall or have sharp edges, which naturally makes lightning arresters susceptible to strikes due to their placement on rooftops or high points. The effectiveness of a lightning arrester lies in its ability to conduct the immense electrical energy of a lightning strike harmlessly into the ground, protecting the structure and its occupants from potential damage and danger.

Lightning rods, or lightning conductors, work based on the principle of providing a preferred path for lightning strikes to safely discharge their electrical energy to the ground. A lightning rod is typically a metal rod or conductor installed at the highest point of a structure and connected via a conductor to the ground. When lightning approaches, the rod and its connected system present a low-impedance path for the lightning’s electrical charge to follow, effectively guiding it away from the structure’s sensitive components and reducing the risk of damage or injury.

A lightning arrester (or surge arrester) functions by quickly diverting excessive voltage surges, such as those caused by lightning strikes or switching operations, to the ground. The arrester typically consists of a series of metal oxide varistors (MOVs) or other semiconductor components connected between the power line and ground. Under normal operating conditions, the arrester presents a high impedance and does not conduct current. However, when a voltage surge exceeds a certain threshold, such as during a lightning strike, the arrester clamps down on the surge by becoming conductive, diverting the excess current safely to ground and thereby protecting connected equipment from damage.

If a surge arrester is directly hit by a lightning stroke, its effectiveness in protecting connected equipment depends on several factors, including the magnitude of the lightning strike and the design specifications of the surge arrester. In some cases, a surge arrester may sustain damage or fail if the lightning strike exceeds its rated capacity or if the surge is exceptionally powerful. Modern surge arresters are designed to handle high-energy surges, but a direct hit by a lightning stroke could potentially overwhelm even the most robust surge protection systems. Proper installation and maintenance of surge protection devices are crucial to ensure they can effectively mitigate the impact of lightning strikes and other electrical surges on sensitive electronic equipment.

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