Lightning arrestors, its features and specifications

A lightning arrester is a device used to protect the insulation and conductors of a system from the damaging effects of lightning. A lightning protection system’s purpose is to ensure safety to a building and its occupants if lightning happens to hit it directly, a task accomplished by providing a good, safe path to ground for the lightning to follow. The lightning arrester is located close to the equipment that is to be protected (on the roof near the PV power plant for example). They are usually connected between phase and ground in an AC system and pole and ground in case of the DC system.

Components of a lightning protection system

A lightning protection system is composed of three main components as mentioned in the below image:

  1. Rods or Lightning Rods or Air Terminal– The small, vertical protrusions designed to act as the ‘terminal’ for a lightning discharge. Rods can be found in different shapes, sizes and designs. Most are topped with a tall, pointed needle or a smooth, polished sphere.
  2. Conductor Cables – Heavy cables that carry lightning current from the rods to the ground. Cables are run along the tops and around the edges of roofs, then down one or more corners of a building to the ground rod(s).
  3. Ground Rods – Long, thick, heavy rods buried deep into the earth around a protected structure. The conductor cables are connected to these rods to complete a safe path for a lightning discharge around a structure.

Lighting protection, standards for lightning protection system, the working principle and design method (Protective angle and Rolling sphere method) are well explained in the video by NPTEL.

Video copyright and property of  NPTEL-NIGHT IITM (Youtube)

Lightning arrestors in Solar PV Power Plants

Lightning can be destructive even when it’s not a direct hit. Indirect lightning events generate an electromagnetic force that induces overvoltage and transients on AC and DC power conductors. The energy released by a lightning discharge is one of the most frequent causes of the fire. Therefore, personal and fire protection is of high importance in case of a direct lightning strike to the building.

At the design stage of a PV system, it is evident whether a lightning protection system is installed on a building. Some countries’ building regulations (Including India) requires that the buildings should be equipped with a lightning protection system, however, in the residential sector, this is not commonly implemented during the construction of the building.

Generally, the installation of PV modules does not increase the risk of a lightning strike. Therefore, the request for lightning protection measures cannot be derived directly from the mere existence of a PV power plant. However, substantial lightning interference may be injected into the building through these systems. Therefore, it is necessary to determine the risk resulting from a lightning strike as per suggested technical standards and to take the results from this risk analysis into account when designing and installing the PV power plant. In India, the installation of the Lighting protection system is required to be done as per IS 2309: Code of practice for the protection of buildings and allied structures against lightning (https://law.resource.org/pub/in/bis/S05/is.2309.1989.pdf). Other IEC standards for Protection against lightning is IEC 62305: 2020 SER Series.

 

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