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Martin, M.A. Lightning: Where Does It Go, What Can It Do? Inside Fire. Volume 7. Spring 1998.

Abstract: This article explains what happens to lightning after it strikes the ground. The energy from the lightning hits the ground and travels along the earth until the energy level reaches zero. Sometimes the propagation of a lightning strike in the remote ground can cause electrical problems. All electrical power is connected to remote ground and the traveling energy from a lightning strike can cause over-voltages. If the over-voltages of all the utility grounds in one building reach the same level, there should be no damage. When the over-voltages occur unevenly in one building, dangerous voltages can cause fires, electric shock, or electrical failures.

The problem posed by transient over-voltages has increased in recent years due to many building being connected via computers, fax machines, and modems. This requires that connections and bonding follow the new National Electric Safety Code (NESC) and National Electric Code (NEC) which states that, "all utilities bond the grounds at one location at one service point." However, these new standards do not help homes and buildings built before the code changes. The article explains, in detail, an example of a home built prior to 1970, which used surge protectors for equipment like computers and cable lines. The bonding was completed incorrectly causing differences in the ground potential. This almost caused the surge protector to ignite. The bonding of all buildings and homes must be correct to prevent utility grounds rising unevenly above the remote ground, as a result of transient energy from a lightning strike.

Inside Fire is out of print. For information on obtaining articles from back issues, contact:
National Emergency Training Center
Learning Resource Center
16825 South Seton Ave.
Emmitsburg, MD 21727
Phone: 1-800-638-1821 or (301) 447-1030
Web Site: www.lrc.fema.gov

 
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