Materials and Construction of Lightning Arresters on a House

Lightning arresters, also known as lightning rods or lightning protection systems, are critical components in safeguarding residential structures from the destructive effects of lightning strikes. These systems consist of several key materials that work together to ensure safety and effective protection. This detailed guide will explore the various materials, their properties, and the construction process of a lightning arrester.

Key Materials in a Lightning Arrester

Conductor Rods

Conductor rods are one of the essential components of a lightning arrester. Made from highly conductive materials such as copper or aluminum, these rods are installed at the highest points of a structure. Their primary function is to intercept and guide lightning strikes away from the building and safely to the ground. The choice of these materials is crucial due to their high conductivity, which ensures that the electrical charge from the lightning can be safely transferred to the grounding system.

Grounding System

The grounding system in a lightning protection system includes ground rods or plates. These are typically made from materials such as copper or galvanized steel, which are known for their durability and resistance to corrosion. These materials are buried in the ground and act as a pathway for the electrical charge to dissipate safely into the earth. The effectiveness of the grounding system is vital as it ensures that the shock of the lightning strike is distributed harmlessly through the ground rather than through the structure itself.

Connectors and Bonding Materials

Connectors and bonding materials are used to link different components of the lightning protection system. These materials, often made from copper or aluminum, are chosen for their excellent conductivity and durability. They facilitate the creation of a continuous conductive path from the conductor rods to the grounding system, ensuring that there are no interruptions that could otherwise compromise the system's effectiveness.

Down Conductors

Down conductors are heavy-gauge copper or aluminum wires that conduct the electrical charge from the conductor rod to the grounding system. These wires are crucial as they play a direct role in safely transferring the lightning’s electrical charge to the ground. The high conductivity of these materials ensures that the lightning surge is efficiently channeled away from the structure, reducing the risk of damage.

Surge Protection Devices

While not always part of the physical lightning rod itself, surge protection devices (SPDs) are often included in a comprehensive lightning protection system. These devices are designed to protect electrical systems from surges caused by lightning. SPDs are typically installed at key points in the electrical system to divert any excess electrical energy away from sensitive equipment and protect against potential damage.

Mounting Hardware

Mounting hardware consists of brackets and clamps made from corrosion-resistant materials such as stainless steel. These components are used to secure the conductor rods and conductors in place, ensuring that they remain fixed and do not move during severe weather conditions. The mounting hardware is crucial for maintaining the structural integrity and safety of the lightning arrester.

Construction and Function of Lightning Arresters

A lightning arrester operates by becoming an efficient electrical conductor when subjected to excessive voltage. Under normal conditions, a lightning arrester acts as an insulator, but during a lightning strike, it can rapidly become a conductor, providing a path for the lightning surge to dissipate harmlessly into the ground.

Early Lightning Arresters

One of the earliest forms of lightning arresters were simple metallic spark gaps. These spark gaps were often V-shaped. As the voltage increased, the gap would break down, allowing electricity to flow, thus diverting the lightning away from the structure. However, this design was limited in its ability to handle large surge currents, and it often required spark gaps to prevent overheating of the metallic components.

Modern Lightning Arresters

In the mid-1930s, silicon carbide arresters were introduced, featuring a series of sintered silicon carbide disks connected in series with small spark gaps sealed within a ceramic or clear Pyrex glass housing. While effective, these devices required series spark gaps to prevent overheating due to continuous AC current flow.

Modern arresters utilize Metal-Oxide Varistors (MOV) made from sintered zinc-oxide disks. In the OFF condition, these components conduct little AC current, making them more reliable and capable of handling large transient surge currents. Following a lightning strike, the MOV rapidly conduct the surge current and recover quickly, returning to their OFF state. This design eliminates the need for series spark gaps and provides a more efficient and reliable solution.

Conclusion

The materials and construction of a lightning arrester play a crucial role in ensuring the effectiveness and safety of the system. By using highly conductive materials such as copper and aluminum for conductor rods, grounding systems, and down conductors, and reliable components such as MOVs for surge protection devices, these systems can provide robust protection against the destructive power of lightning.

For more detailed information and images of lightning arresters, refer to the provided links and resources.