Lightning has always been one of the most intense natural forces, harnessing tremendous amounts of energy capable of destroying buildings and unprotected equipment in seconds. Each year, lightning is responsible for $4 to $5 billion in damage costs in the U.S., with over twenty million recorded strikes. Historically, lightning rods have been used to provide a means of protection by establishing a low resistance path to ground that can be used to conduct the enormous electrical currents that occur with lightning strikes. If lightning strikes, the system attempts to carry the harmful electrical current away from your home and safely to ground.
The idea of the modern day lightning arrester evolved from the lightning rod, but takes advantage of a unique material characteristic to provide additional equipment protection. A lightning arrester is used to protect electrical lines and electrical equipment, a somewhat different function than a lightning rod that can protect buildings and other structures.
Essentially, a lightning arrester is an in-line circuit device whose characteristics change during an excessive voltage surge, so the path of least resistance is through the arrester and not through the piece of equipment or the circuit that it’s designed to protect. The excess energy is discharged to ground. The lightning arrester works by using a gas-filled gap that acts as an open circuit to low potentials, but becomes ionized and conducts at very high potentials. If the lightning hits a particular electrical line that is protected with an arrester, the gas gap will conduct the current safely to the ground.
Lightning arresters are a relatively inexpensive solution used on all types of buildings, particularly in regions of the country with lots of lightning activity. They can be used in combination with other surge protection devices to handle a broad range of electrical surges. Surge protectors by themselves typically provide protection for power surges in the line within a home or from the power company, but do not have the capacity to handle a nearby lightning strike. Lightning arresters must be used to help divert the extraordinary energy of a lightning strike, and even then, they may not be capable of handling a direct hit.
In order for surge protection equipment to work properly, it is critical that the home have a good, low-resistance grounding system, with a single ground reference point to which the grounds of all building systems are connected. Without a proper grounding system, surge protection becomes quite difficult. The NLSI provides guidelines and recommendations for surge protection of buildings, and the National Electric Code (NFPA 70) can be consulted on grounding issues as well.
Modern homes 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. Devices that are tied to phone or network lines should use surge protectors with protection ports for phone and network connections. The purpose of the arrester is only for lightning protection. The meter-based or panel-mounted protector can handle high energy power surges that enter through the electric service. Smaller plug-in protectors provide secondary defense at the equipment to guard against internal surges and surges that may come through non-electric lines (like computers or large screen televisions).
Lightning arrestors are already installed on transmission and distribution lines to mitigate the effects of strikes on the system. However, the system lightning protection that works to protect the utility grid does not have the capability to protect every point on the network. This is why customers in areas that are prone to lightning strikes will install their own lightning protection to add another layer of protection. One hundred percent protection is probably impossible, as well as cost-prohibitive.
As a matter of interest, Florida tops every other state with an average 1.3 million lightning flashes a year, or about 20 flashes per square mile. North and South Carolina average about 3/4 million flashes or 10.8 flashes per square mile.