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Strube, Dann. Understanding Grounding As a Firesafety Necessity. Fire Journal. January/February 1989. p. 62+

Abstract: This article explains the importance of grounding systems and how their malfunction can result in fire. Many insulation failures are mistakenly identified as short circuits, when they are really ground faults. A ground fault is a failure between a conductor and a grounded surface. A short circuit is a failure between two circuit conductors.

When a short circuit occurs, the over-current protection device will promptly open the circuit, which results in very little damage. A ground fault can cause much more damage, especially if the equipment is installed properly. A malfunctioning return path can cause an arcing ground fault that could continue for a long period of time, eventually igniting combustibles. This heating can cause insulation of other conductors to fail, causing a short circuit. Investigators are quick to blame the short circuit for the fire. However, if the short circuit had occurred earlier, the over-current device would have opened the circuit, preventing the fire. The real blame is the ground fault.

The article explains other situations when ground faults result in fires. In order to prevent this, section 250-251 of the National Electric Code provides safety requirements for grounding electrical equipment. The ground path must be permanent and continuous. It must have the capacity to safely conduct the fault current that will be imposed on it. It must also have low impedance to limit the voltage and allow the protective devices to operate.

For more information, contact:
Fire Journal is now NFPA Journal and published by the National Fire Protection Association (NFPA)
Call the NFPA Library at (617) 984-7445 or e-mail library@nfpa.org

 
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