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What is a Lightning Arrester?

Mary McMahon
Updated: May 17, 2024

A lighting arrester is a piece of equipment that is designed to protect electrical systems and components from damages that can be caused by surges of electricity. Such surges can be the result of lightning or electrical switching and can be very dangerous, especially for electronics like computers. Utilities fit their power lines with lightning arresters, as well as other safety measures and these devices can also be mounted on individual electrical boxes.

When a surge of electricity hits an electrical system, it attempts to equalize and dissipate itself, taking the most efficient routes. A lightning arrester provides a path of least resistance for doing this, routing the excess electricity away from the system and into the ground where it can dissipate without doing any harm. The lighting resistor includes components attached to the electrical system with leads that reach the ground.

Soft, clay soils tend to be ideal for grounding, although other soil types can be used in a pinch. The resistance of the soil should be measured before a lightning arrester is installed to find an area with resistance that is as low as possible. This will allow the electricity to quickly flow out through the lightning arrester before it has a chance to enter the system and damage either the system or its components.

For utilities, there are concerns about lightning damaging insulation and other components on power lines. The lightning arrester has one terminal that is designed to handle very high voltage, and another terminal connected to the ground. On a home electrical box, similar systems are used although they are of a somewhat smaller scale. A licensed and experienced electrician needs to be involved in installation to confirm that the lightning arrester is installed, connected, and placed correctly. Installing it incorrectly or failing to maintain it can create a safety risk.

Lightning arresters are not the same thing as lightning rods. Lightning rods are used to protect entire buildings and other structures from lightning damage. They are placed with the goal of getting lightning to strike the rod first and dissipate out through a grounding cable. This prevents lightning from hitting the structure itself and causing a fire or other types of structural damage. It is possible for a structure to have both rods and arresters, along with other lightning protection measures. Insurance companies may require or strongly recommend redundant lightning protection, as do some safety organizations.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By MrMoody — On Aug 31, 2011

@Charred - You can also get a surge arrester as well, which is basically like a lightning arrestor. I would recommend a surge arrester for high voltage situations, in tandem with the surge protection you mentioned.

I don’t know that a surge protection unit alone would offer the same kind of safety in a really high voltage situation, so I would use both of them for ultimate protection.

You can buy surge protectors fairly cheaply and install them in various locations in your house, close to areas where you know you will have good grounding.

By Charred — On Aug 30, 2011

I have had two lightning strikes hit the vicinity near our house on separate occasions. I cannot say for sure whether or not we took a direct hit in either case, but it sure felt like it.

Anyway, in the first storm it completely blew out our big TV’s picture tube, and it was a nice TV to boot. In the second storm, the strike took out an electrical socket in the house and also part of the computer – the Ethernet port on the motherboard.

I know this because thereafter I was no longer able to connect to the Internet, even after switching to a new cable modem (I thought it was the modem that was bad at first).

The lesson learned from both of these instances is that you should make sure that you have a decent surge protector to protect your valuable electronics.

By stl156 — On Aug 30, 2011

@Izzy78 - I understand your question. Although lightning arresters are designed to protect electrical systems from lightning damage, Mother Nature is impossible to predict.

Just like a tornado, lighting is a wonder of Mother Nature that is very unpredictable and impossible to estimate the potential damage beforehand. I like to think that a lightning arrester is something that is a last ditch effort to save the electrical system, and probably is fairly effective. However, I can never see something being one-hundred percent effective against something as intense and unpredictable as a lightning strike.

By Izzy78 — On Aug 29, 2011

I have never fully understood lightning arresters. These are designed to save electrical systems from a lightning strike, somewhat like surge protectors on a smaller scale, but it is very hard to protect from something as incredible as a bolt of lightning.

Although people think that lightning rods can protect building from damage they are only designed to protect the outside of the building and maybe even protect from starting a fire on the roof of the building.

Whenever the power goes out in my town due to a lightning strike, the power goes out and that is that. I do not understand or know how effective lightning arrester's are but I wonder if they are just something that is there as a last ditch effort to save the electrical systems.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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