1 Lightning Rod Manufacturers in 2022

What Is a Lightning Rod?

A lightning rod is a structure that protects electrical equipment and the human body from lightning strikes. They are made of needle-shaped metal and installed vertically on the ground.

In the power system field, lightning rods are mainly installed in outdoor substations, etc., and protect equipment from direct lightning strikes by directing lightning strikes to the lightning rod instead.

Although there are also "lightning arresters" that also serve as lightning protection equipment, they are not synonymous with lightning rods. Lightning rods prevent lightning from striking people and buildings, whereas lightning arresters protect electrical equipment from malfunctioning when it is near the point of lightning strikes.

Uses of Lightning Rods

Lightning rods are installed to prevent damage to electrical equipment and people caused by lightning strikes. The following are examples of buildings where lightning rods are installed.

• Areas with buildings, including  low and high-rise buildings
• Hazardous material storage areas and tanks

Hazardous material storage areas and tanks are mainly located on building rooftops. Hazardous material storage tanks are often installed to prevent leakage and fires caused by lightning strikes. Lightning rods are connected to grounding poles with conductors that can withstand high currents and are designed to channel lightning strikes into the ground in this case. 

Principle of Lightning Rods

Lightning rods are made of stainless steel or titanium. The reason is that they are highly conductive and can withstand corrosion caused by strong winds and rain.

Lightning clouds have positive and negative charges, with positive charges distributed at the top of the cloud and negative charges at the bottom. When a positive charge is distributed at the tip of a lightning rod, the negative charge at the bottom of the thundercloud and the positive charge of the lightning rod is attracted to each other, and lightning strikes are guided to the lightning rod.

Since the positive charge is stored in objects directly under the thundercloud, positive charge is inevitably stored at the tip of the lightning rod. Therefore, artificial measures to store positive charge in the lightning rod are unnecessary.

In addition, the lightning rod must be securely grounded because the charge induced by the lightning rod must be safely discharged to the ground.

Other Information on Lightning Rods

1. Lightning Rods and PDCE Lightning Rods

Lightning rods are generally installed on the roofs of buildings. In Japan, lightning is concentrated in July and August. This is because charged cumulonimbus clouds tend to develop during the summer due to updrafts.

In cases with no tall buildings around, lightning rods may be installed on isolated houses. However, since lightning rods are installed to be targeted by lightning strikes, it limits damage to the structure but cannot eliminate it.

In recent years, there have been lightning protection and lightning dampening (PDCE) rods, which are designed to avoid lightning strikes. This is based on the difference in electrical charge between the thundercloud's negative pole and the ground's positive pole. By controlling the top of the lightning rod to the negative pole, lightning that would otherwise pass through the rod will avoid the rod and more easily strike the ground. 

2. Lightning Rod Installation Standards

Lightning protection equipment, including lightning rods, is a structure for which standards are established by the Building Standards Law, the Fire Defense Law, and the Electric Utility Law.

The Building Standard Law requires installing lightning protection equipment on buildings over 20 meters high and on structures such as chimneys, advertising towers, and flight towers. However, this does not apply to buildings as long as the surrounding conditions do not pose a safety hazard.

Even if a building is less than 20 meters, there is a possibility of a direct lightning strike if there is nothing around it. For this purpose, The Building Standard Law establishes an index for each of the following: the purpose of use of the building, structure of the building, contents of the building, degree of isolation, topography, and height. The decider is whether the total reaches 40 or more on the index. 

The Electricity Business Act also stipulates periodic inspections and safety regulations for photovoltaic power generation and generators, including lightning rods. The law stipulates that the grounding resistance installed in lightning protection equipment should be 10 ohms or less.