Ground Bars and Electrical Power Systems

Ground bars are very important parts of an electrical power system. They are misunderstood in their purpose and are often overlooked when specifying a new installation. In practice they look like simple copper bars with holes. They are actually a very vital piece of equipment and serve as a safety device for all electrical systems. Every electrical service system must have ground bars, not just because some rule says so, but because they are needed for proper safe operation of the system.

Ground Bars

The ground connection establishes a common reference potential for all components attached to it. It makes sure that in the event of a live conductor contacting a part of a component to which humans may be exposed that potential is pulled down to ground potential in effect a short to ground. In most instances such a hard short to ground will cause a breaker to open or a ground-fault detector to trip protecting personnel. Without a proper ground, a ground-fault detector will not work. Without the common ground connection it is possible for a metal part of a machine or electrical device to become energized with hazardous potential. The size of the wire connecting a component to a grounding system is important. The ground wire should be able to carry the same current as the wiring to the component so that in case of an unintended ground contact the ground current will be enough to trip the breaker of blow the fuse protecting the component.

Ground Bars the Grounding Point

Without a common grounding point, grounding can daisy-chain through connected devices and components creating a ground loop. Ground loops are dangerous to equipment and can cause erratic operation. People have been injured when equipment was installed without proper grounding or when grounding systems were compromised. A piece of equipment can become energized in relation to another piece of equipment nearby. When a person comes in contact with the two parts with different potential a shock occurs. This will cause injury or even death. Proper grounding prevents this scenario.

Almost all electrical cabinets are furnished with some kind of grounding system. These are generally supplied by the utility cabinet maker as part of the assembly. Custom cabinet manufacturers often manufacture custom ground bars for the cabinets they build. Other ground bars are made to customer specifications to be included in existing electrical boxes or private projects.

There are Underwriters Laboratories (UL467) and CSA (22.2) standards for grounding systems. Most engineers refer to these standards when specifying grounding and bonding for electrical components or systems. There is also an NEC standard (NEC 250) related to the UL standard. It addresses the use of dissimilar metals and the related galvanic corrosion that can occur.

There are companies that specialize in manufacturing custom grounding devices and components. The engineers at these companies are the best sources of information about grounding. They can help the specifying engineer design a proper grounding system for any application. The proper ground bars, properly installed will assure long term safety and operation.