Understanding Your Ground System

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Connect Power wants to help educate our neighbors on how to keep themselves safe on our docks here at the Lake of the Ozarks. 

You might be saying my dock is safe, I or had it wired it to code. Even with the proper equipment, electrical safety devices installed on your dock, if your electrical ground system in your home isn't up to par you, your family, and your neighbors can be at risk. 

Grounding is the most important aspect of electrical or electronic system design. Improper grounding results in damage to the property and great risk for inhabitants of homes and on our docks. Here at our Lake, it is a big responsibility to ensure our dock is safe. Liability is something we all share for being waterfront property owners

A ground is a conductive connection between the earth or other conductive material in the place of earth and an electric circuit or a piece of equipment.

 The principle reason for facilitating the grounding is to enable immediate diversion of heavy fault current in the event of a circuit fault, thereby protection is provided against electric shock hazards to people and animals. 

In grounding or earthing, an electric circuit or apparatus is connected to the earth by a metallic conductor of negligible resistance. This conductor should have good conductivity, high tensile and rupturing capacity, and must be of corrosion or erosive resistance.

The earthing is classified into two major types, namely, system or neutral grounding and equipment grounding.

There are several types of grounding electrodes found in homes.  At least one of these methods should be present in any home regardless of age, and newer homes usually require multiple methods—-redundant methods. Having a connected ground rod system at all electrical service panels.  The entire electrical ground system should all be connected together. Reducing the possibility of electrocution from the principalimproper ground. 

The very newest of homes will likely have only one means of grounding.

I know this seems confusing, but ground requirements have evolved over time accounting for all the various methods that will be found in homes of all ages.

Historically, the original method of achieving grounding was the water pipe coming from the street.  The next method to be employed is a single ground rod.  After this requirement, two rods driven 6 feet apart became the norm.  Now a third method called an “Ufer Ground” is required in many jurisdictions.  With this grounding method, the entire rebar system of the concrete foundation is utilized.  This method is far superior to all of the other methods,  ensuring an effective ground.

As we discussed above that grounding is mainly classified into two types as system grounding and equipment grounding. Let us discuss these types in brief.

System or Neutral Grounding

The major consideration in a neutral grounding system is to provide safety to human beings and to maintain the safe working of electrical appliances, under the assured operation of the protective relay system.

This offers improved service reliability, greater safety, reduction of transient voltages, and improved fault protection. The commonly used methods of system grounding include

In this, the neutral conductor is directly connected to the ground without any impedance between the neutral and earth. It is a simple and inexpensive method that requires no extra equipment.

It minimizes the overvoltage in the faulty phase during a phase to a ground fault which results in the reduction of stress on insulation on the faulty conductor. This method is most commonly used in industrial and commercial power system operations. The disadvantage of the solid grounding is that severe flashes or arcing hazards are caused during high line to ground faults. Lightning is an example. These arcs may cause the burning of protective devices.  

As discussed earlier that connecting metallic enclosures or non-current carrying metal parts of the electrical equipment to earth is called equipment grounding.

Consider that electrical equipment of resistance R is connected across the supply mains and assume that it is not grounded or earthed. Let B be the resistance of the body of a person who touches the apparatus while maintaining contact with the earth.

The current from the electrical main panel has two paths; one path is through the apparatus and the other through insulation resistance of the apparatus next resistance Rb of the body and finally through earth resistance to the neutral of the supply.

If the insulation resistance is infinity, no leakage current flows through the body and hence no shock is experienced by the person.

If the insulation of the apparatus is failed or defective, the insulation resistance becomes zero and hence the leakage current from the electrical main panel passes through the body of the person and its magnitude depends on the body resistance. This current is quite sufficient to give a shock to the person.

If the equipment enclosure is connected to the ground neutral wire, the leakage current flows through the enclosure and back to the neutral wire in case of insulation failure.
Therefore, the equipment is maintained at earth potential and the person or operator would not experience any shock as the leakage current is diverted to the neutral ground path.

This method is not safe because if by any chance the neutral is opened under the fault condition, the person in contact with the enclosure would receive a severe electric shock.
Suppose, the equipment is grounded with separate ground wire such that the path offers zero resistance to the current flow.

When the person touches the equipment in the event of insulation failure, the fault current is diverted through the ground path rather than through the body of the person. Hence the severity of the shock is avoided by this equipment grounding.