My article in the September issue of ELECTRICAL CONTRACTOR, “Dodging the Bolt,” was about lightning strikes at two residences and produced discussions with several readers.

One noted an error, where the typical lightning strike should have been 30–40 kA, but I lost the kilo somewhere in my editing process. Also, there were actually two separate incidents. The one illustrated with the pictures was not the one where the homeowner using a power tool in his garage was electrocuted from a lightning strike. The good news on the latter is that his hospital stay was not very long and he has recovered.

Notify the fire department

Joe Ferry, a master electrician in South Jersey, provided some good insights from his experience on lightning strike results. A potential problem that should not be ignored relates to hidden damage to equipment and the electrical infrastructure after a lightning strike. The more explosive images in the article showed the obvious destruction. But was the insulation of the wiring inside the walls compromised? Lightning is powerful enough to cause insulation and wires to melt, as well as pyrolysis of plastics and wood to lower their ignition point.

As Ferry pointed out, the first step, regardless of whether there is smoke, is to notify the fire department so a fire incident report can be made. Also, have them take a look throughout the structure for problems.

A retired fire chief who had responded to many lightning incidents in his 40-year career added that thermal imaging cameras are an effective tool for the fire service to see inside walls and ceilings without opening them up to look for indication of possible fire. 

Coincidence or not, he had just experienced a lightning-related incident in his own residence a few days before we spoke. A simultaneous brilliant flash and deafening sound led him to investigate his house, finding that a breaker for his kitchen refrigerator circuit and another for his detached garage tripped. The garage circuit was a GFCI breaker, which may have been tripped due to the different voltage levels induced in the ground and his electrical system by the lightning strike. A weather app indicated that the recorded strike was a block away, but lightning can have multiple leaders.

The next step after experiencing a lightning event, whether a direct strike or coupled through the power lines, would be to contact the insurance company and request that the damage be covered and costs for wiring insulation impedance tests be made by a qualified electrician. These are often referred to as a megger test, as the readings are in the megaohm levels. If the insurance company pushes back, the state fire marshal might help to explain the need for such, provided there is a fire incident report on record.

Lightning myths and risks

The National Oceanic and Atmospheric Administration debunks a number of myths about lightning, including that it never strikes twice, that crouching down outside makes you safer and the idea that victims store electrical energy. A lot of factors go into where and when lightning will strike. Since lightning is nature’s circuit maker to neutralize large potential differences in electrical charge, things that keep the energy away from structures, such as lightning rods and not using electrical equipment, are risk reducers.

One risk in the past that has diminished significantly is talking on the phone. Phone wires associated with landlines are an electricity conductor, including lightning. Cellphones have decoupled that path, though I imagine someone has a theory that the electromagnetic field surrounding a cellphone could attract lightning.

This ground and that ground

As lightning protection systems incorporate ground rods, it’s important to distinguish between this ground and that ground. They have their own grounding electrode system, along with strike termination devices, cable conductors and surge-protection devices, which are covered in detail in NFPA 780, Standard for the Installation of Lightning Protection Systems. Bonding or the interconnection of the lightning protection system to other internal grounded metallic systems must be accommodated to eliminate the opportunity for lightning to side-flash internally, but it must be done according to the standard.

This brings us to one final myth—that the pointed tip of a lightning rod (or strike termination device) will bleed off the charge in the area and prevent lightning from striking. While the tip is capable of ionizing the surrounding area, it’s only an area of a few meters, versus the kilometers of distance of charge in the cloud above.

It’s often said that lightning doesn’t really know where its going to strike until the last 50 feet of its path. When it does decide, its best to have a system that can keep that massive amount of energy away from harming anyone or anything.

stock.adobe.com / Sergey Nivens