Lightning-Induced Surge on Cable Wiring

Quote of the Day

People seldom improve when they have no other model but themselves to copy.

— Oliver Goldsmith, writer. I love to read biographies. I often look to these biographies for inspiration on how to approach my work and home life.


Figure 1: My Favorite Lightning Photo. Notice
the lightning jumping from the hub cap to the
ground. Even the insulation of the tires did not
stop the bolt from reaching ground. (Quora)

Because I have had to deal with lightning in all sorts of contexts (e.g. military equipment, commercial hardware, consumer products), I have developed an enormous respect for the power of lightning (Figure 1). Because of this respect, I have worked to ensure that my own home has excellent lightning protection, including a sophisticated ground system. Even with all my precautions, last weekend lightning struck near my home and caused my garage door to open – letting rain into the garage, and my garage door opener to become unresponsive. Fortunately, I just had to cycle power again on the garage door opener and it started to work.

This week, a friend sent me these photographs from a fire investigator who was preparing a report on a lightning surge on a home's cable TV wiring. I thought some of you may find these photos interesting. If you are looking for more information on lightning protection, see this post.

In Figure 1, you see where the cable passed through some joists that had fiberglass batt insulation between them. During the lightning strike, the cable became very hot.

Figure 1: Region of Ceiling Where Cable was Run.

Figure 1: Region of Ceiling Where Cable was Run.

In Figure 2, you can see the soot rising above the cable penetration through the joist.

Figure 2: Close up of Joist With Coaxial Cable Running Through It.

Figure 2: Close up of Joist With Coaxial Cable Running Through It.

In Figure 3, you can see more soot on the fiberglass batts.

Figure 3: Soot on Fiberglass Batts.

Figure 3: Soot on Fiberglass Batts. You can see why it is important to consider the flammability of building materials, like insulation.

 
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