What is a Lightning Arrester in substations and Why is it used?

A Lightning Arrester, also referred to as a surge arrester is a protective device designed to divert excessive lightning currents away from sensitive electrical equipment and structures. Its primary objective is to safeguard against the destructive consequences of lightning strikes, preventing damage to power lines, transformers, and other vital components of an electrical system.

The use of Lightning Arresters is imperative due to the unpredictable and potentially catastrophic nature of lightning strikes. When lightning occurs, it generates immense electrical energy that can travel through power lines and other conductive pathways, leading to electrical surges. These surges can damage or destroy electronic devices, appliances, and even entire electrical systems.

Unlike lightning rods used in residential and industrial settings, which are designed to intercept and safely ground the lightning strike, a substation LA operates differently. It remains “open” to the system voltage under normal operating conditions, meaning it does not conduct current to the earth. However, when a voltage surge occurs, the LA “closes”, becoming a low resistance path to the earth, thereby bypassing the surge voltage and protecting the substation equipment. This is particularly important in substations, as they are often connected to high voltage transmission lines, at the first point of entry into the substation. Since these lines are highly susceptible to lightning strikes, making the role of the LA in a substation critical for maintaining the reliability and safety of the power system.

Protection against other electrical surges: Lightning Arresters not only guard against direct lightning strikes but also provide protection from other electrical surges that may also occur. Instances like the contact between a high-voltage line and a low-voltage line, or the breaking of high-voltage lines that subsequently fall onto other lines during a high-voltage line goes cross, etc. that can result in abrupt voltage surges. Lightning Arresters act as a line of defense, diverting and suppressing these unexpected surges, thus preventing potential damage to connected equipments.

Functions of Lightning Arresters

Diverting lightning currents: Lightning Arresters function by providing a low-impedance path for the lightning current to follow. This diversion prevents the electrical energy from flowing through the protected system, thus avoiding potential damage.

Absorbing and dissipating energy: Lightning Arresters are equipped with materials capable of absorbing and dissipating the energy generated during a lightning strike. This helps in reducing the impact of the surge on the connected electrical infrastructure.

Maintaining system integrity: By diverting lightning currents away from the system, Lightning Arresters contribute to maintaining the integrity of electrical networks, preventing downtime and costly repairs.

Lightning Arresters play a pivotal role in safeguarding electrical systems and structures from the destructive forces of lightning. Their ability to divert, absorb, and dissipate lightning currents ensures the reliability and longevity of power distribution networks, infrastructure, and various other applications.

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