What is a lightning arrester and how to select a lightning arrester

What is a Lightning Arrester

A lightning arrester is protective devices to protect the equipment from lightning surge voltages due to lightning strikes while using it there won’t be any disruption of service because it will protect the equipment. It is also called as surge arrestors.

It is a device which is used in electrical power systems to protect the insulation on the system from the damaging effect of lightning, in earlier day metal oxide varistors are used for power system protection. a lightning arrester has a high voltage terminal and ground terminal


What is a Lightning rod or Lightning conductor

It is a rod or conductor which would be mounted on the top of the building or tower and then electrically connected to the ground by using a wire and it will protect the building or equipment in case of lightning

A lightning arrester is a diverter connected in parallel or shunt with the equipment to be protected

  • It will conduct at a voltage above diverter rating
  • It will restrict the voltage across its terminal to the design value
  • It will become non-conducting when the line to neutral voltage becomes lower than the design value

What exactly does a Lightning arrester do

  • It does not absorb the lightning
  • It won’t stop the lightning
  • It diverts the lightning to the ground
  • Arresters limit the voltage produced by the lightning
  • Lightning arresters equipment will be electrically in parallel with it

Working of a Lightning arrester

In all the lightning arresters a Metal oxide varistor is used, the MOV is a semiconductor which is sensitive to voltage. At normal voltage, MOV disk is an insulator and will not conduct current, but in higher voltages which would be created by lightning or any surges it will become a conductor

The MOV disk will be placed in porcelain enclosure to provide physical support and heat removal and it will be sealed for isolation from contaminating in the electrical environment

While an electrical system is hit by a surge of electricity, it would seek to equalize and dissipate as quickly as possible and it will take the path of least resistance, and thus by using a resistor the electrical surge can be diverted from equipment insulation and then it will be channeled to the ground through grounding rods, so to do this the resistor uses a metal oxide varistor

Difference between lightning arrester and surge arrester

A lightning arrester will divert the lightning to the ground alight lightning arrester will be placed on the top of the building or tower because the lightning will hit in places where there is a conductor, while the surge arresters are used in a circuit which will protect it from surge voltages and current.

Types of lightning arrestors

Station class

It is mostly used in an electrical power station or substations and other high voltage structures, this arrestor will protect against all types of overvoltages and lightning when the electrical devices have more current in the system than it is designed to handle. It is used to protect the equipment which is above 20mVA range

Intermediate class

It will also protect the equipment from electrical surges caused by the lightning and overvoltages it is designed to use in medium voltage equipment areas. Such as electrical utility stations, substations, or other substation equipment. It is designed to use in the equipment which ranges from 1-20mVA

Distribution class

It is commonly used in transformers both dry type and liquid-filled. It is used in equipment which is rated at 1000KVA or less, it is used in exposed lines which have a direct connection to the rotating machines.

Secondary class

These type of lightning arrestors are designed to protect most homes and other buildings from lightning and are required by most electrical codes. This voltage causes high voltage overages to ground, and they won’t short all overvoltage by a surge, it only provides the least amount of protection

How to select a lightning arrestor

It would be better to select a lowest-rated lightning arrester which will provide overall protection of the equipment insulation. A higher rated lightning arrester can’t be used because it increases the ability of the arrester to survive in the power system but reduces the protective margin provides for a specific insulation level

  • It must have satisfactory service life when connected to the power system
  • Minimum rated arrester must be preferred because it provides the greatest margin of protection
  • Selecting the arrester voltage range – it is based on whether or not the system is grounded and the method of system grounding
  • Selecting the class of arrester – the station class arrester provides better protection capability and it is most expensive