Lightning rods are essential equipment that protect condominiums from lightning strikes, but even with one installed, damage cannot be completely prevented. Here we explain what condominium managers need to know about how lightning rods work and their types, installation requirements, lightning surge protection, and inspection and maintenance methods.
What Are the Basic Principles and Mechanisms of a Lightning Rod?
A lightning rod is not designed to "repel" lightning, but rather to "attract" it. Its pointed tip promotes electrical discharge, and an "upward leader" from the ground safely channels the lightning current into the earth. Invented by Benjamin Franklin in 1752, it has over 270 years of history. A lightning protection system consists of three components: an air termination system, a down conductor, and an earth termination system.
What Types of Lightning Rods Are There?
Franklin Rod (Conventional Type)
Installed at the highest point of the building, it attracts lightning via an upward leader and channels the current into the ground. Its protection range is defined by the rolling sphere method.
PDCE Lightning Rod
This is a type of lightning rod designed to prevent lightning from striking. Unlike the conventional type, which actively attracts lightning, the PDCE rod does not induce lightning. It has attracted attention as a lightning-strike-suppression type.
ESE Lightning Rod
The "Early Streamer Emission" type can generate an upward leader earlier than conventional rods. It offers a wider protection range than the Franklin rod and has the advantage of requiring fewer units to be installed.
Ion-Dissipation Lightning Rod
It neutralizes negative charges in the upper atmosphere and positive charges on the ground internally, making it a next-generation type that suppresses the occurrence of lightning strikes themselves. Its protection range covers approximately a 100-meter radius from the installation point. In France, there is a track record of zero lightning strikes in the vicinity over five years of installation.
Is There a Legal Requirement to Install a Lightning Rod in a Condominium?
Under the Building Standards Act, buildings exceeding 20 meters in height are required to install a lightning rod. The 20-meter measurement includes rooftop air conditioning units, signage towers, and chimneys. Even for buildings 20 meters or under, installation is recommended if there are no high-rise buildings nearby or if the area has a high risk of lightning strikes.
How Much Does It Cost to Install or Replace a Lightning Rod?
- New installation: ¥1,000,000–¥4,000,000 (varies depending on building size)
- Repair or relocation: approximately ¥400,000 as a guideline
This includes the costs of earthing work, wiring work, and earth resistance measurement.
What Is a "Lightning Surge" That Can Occur Even With a Lightning Rod Installed?
A lightning surge is a phenomenon in which lightning current penetrates indoors via communication lines or power lines. Even without a direct lightning strike, a voltage of 100,000 volts can potentially be generated from a location 100 meters away. Digital devices such as computers and televisions are particularly susceptible to damage.
Lightning Surge Protection Measures
- Adjusting earth potential to minimize potential differences
- Installing Surge Protective Devices (SPDs)
- Installing isolation transformers to block only lightning surges
What Lightning Protection Measures Should Be Communicated to Residents?
- Use power strips with lightning surge protection
- Attach ground wires to large home appliances
- Unplug power plugs that are not in use
- Regularly back up data
- Stay away from appliances and plumbing fixtures when lightning approaches
Frequently Asked Questions (FAQ)
Q. How often should a lightning rod be inspected?
A. At least once a year is required under JIS standards.
Q. What is the difference between a lightning rod and a surge protective device (SPD)?
A. A lightning rod protects the building and people directly from lightning strikes, while an SPD protects electronic devices from lightning surges.
Q. Can a surge-protected power strip be used repeatedly?
A. Once it absorbs an overvoltage, its protective function is lost, so it needs to be replaced periodically.
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