The earth is conductive to a certain extent, but because of soil resistivity, it should never be considered as an effective path for ground-fault current. The earth is not intended to be used as an effective ground-fault current path for fault detection and/or as a means of operating the overcurrent protection device (circuit breaker or fuse) to clear faults. Connecting to earth and creating a zero reference or zero potential difference eliminates touch potential between conductive surfaces and the earth in theory but is still based on the contact resistance of the earth connection. When there is a potential difference in charges between two points in an electrical circuit expressed in volts, current flow in the circuit will occur. Earth or ground potential is usually considered zero or near zero. The earth connection is also utilized to stabilize the voltage to earth during normal operations. The electrical system is intentionally grounded (connected) to earth in a specific manner to limit the voltage imposed by direct or indirect lightning strikes, line surges, or unintentional contact with higher voltage sources. Grounding (connecting) to earth through an approved grounding electrode or grounding electrode system as described in the 2017 National Electrical Code ( NEC) Section 250.52(A)(1) through (A)(8) serves an important function within the electrical system. The connection of the grounded (neutral) conductor to the EGC provides for the “effective ground-fault current path” to the source such as a generator. The equipment grounding conductor(s) (EGC) are also connected to earth by the same grounding electrode conductor so the potential on the EGC is maintained the same as the grounded (neutral) conductor. The purpose of system grounding is to intentionally connect one system conductor as the “grounded conductor” which is typically a neutral of an electrical system to earth in a manner that controls voltage with respect to the earth within predictable limits. Hopefully, it will clear up any misunderstandings or confusion surrounding the grounding and bonding of vehicle-mounted (trailer) mobile generators. This short article discusses the purpose of system grounding, grounding requirements, separately derived systems, and available short-circuit current.
#ENCASED EMERGENCY GENERATOR PORTABLE#
This is especially true for portable and vehicle, including trailer-mounted generators. The main purpose of grounding and bonding is safety, yet the terms grounding, bonding, and grounded and their respective purpose are frequently misunderstood and misused in the field. That’s why proper installation practices and workmanship apply to both.
Electricity doesn’t distinguish between permanent or temporary installations. Technicians often have an “Anything Goes It’s Temporary” attitude about grounding, bonding, when dealing with the installation of temporary electrical systems and generators on construction sites, industrial facilities, special event venues, and disaster support sites.
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