- Lightning is responsible for more than $5 billion in damages in the U.S. each year.
- Lightning arresters are designed to protect electrical lines and equipment.
- Building protection systems often include a lightning arrester and surge protection devices.
Lightning is one of the most intense natural forces, harnessing tremendous amounts of energy that is capable of destroying buildings and unprotected equipment in seconds. With 15 to 20 million ground strikes each year, lightning is responsible for more than $5 billion in damages across the U.S., according to the National Lightning Safety Institute (NLSI). A Carnegie-Mellon study also showed that one third of U.S. businesses are affected by lightning.
Lightning rods were designed to protect buildings and other structures by establishing a low-resistance path to ground. If a strike takes place, the rod conducts the harmful electrical current away from the structure and safely to the ground.
Lightning arresters, which evolved from lightning rods, are installed on transmission and distribution lines to protect electrical lines and equipment. During a voltage surge, the unique characteristics of lightning arresters change, sending excess energy through the arresters to the ground; providing additional protection for equipment. Lightning arresters do not have the capability of protecting every point on the network, however. Facilities in areas that are prone to lightning strikes add another layer of protection by installing their own surge protection system.
Building protection systems
Lightning arresters are a relatively inexpensive solution used on all types of buildings, particularly in regions of the country where a great deal of lightning activity occurs. When used alone, lightning arrestors provide line protection for power surges within a facility or from the power company, but may not be capable of handling a direct hit. They are useful, however, in combination with other surge protection devices to handle a broad range of electrical surges.
Modern building protection systems may include a lightning arrester and a meter-based or panel-mounted surge protector at the incoming power service. Plug-in or point-of-use protectors should be used to protect sensitive and critical equipment. The purpose of the arrester is lightning protection only. A meter-based or panel-mounted protector can handle high-energy power surges that enter through the electric service. Small, plug-in protectors provide secondary defense at the equipment to guard against internal surges and surges that may come through non-electric lines.
In order for surge protection equipment to work properly, it is critical for facilities to have good, low-resistance grounding systems, with a single ground reference point to which the grounds of all building systems are connected. Without a proper grounding system, surge protection is less effective.
The NLSI provides guidelines for facility surge protection. The National Electric Code, published by the National Fire Protection Association, is a common source for standards and building codes regarding lightning protection and grounding.