In this article, we will explore the difference between grounding and neutral in electrical systems. While grounding and earthing may seem like interchangeable terms, there is actually a nuanced difference between them. It is important to understand the definitions of these terms and the differences between them.
Grounding:
The term grounding is commonly used in the electrical industry to mean both “equipment grounding” and “system grounding.”
When the live part of the equipment is connected to the earth, the potential is known as system grounding. Under normal operation, the potential at the neutral point is zero, and its potential rises during a fault condition. The unbalanced phase currents get added and flow through the neutral point. Thus, the unbalanced/ earth fault current develops the potential rise at the neutral point of the common point of star connection. The rise in the potential at the neutral point causes the current to flow from the neutral to the earthing or grounding point.
The grounding is used for the following equipment.
- Dyn11 vector group transformers are used for distribution purposes.
- The current transformers are used for the protection of the equipment.
System Grounding:
The neutral of the transformer must be earthed to the ground. Solid earthing is used for the equipment with a voltage rating of less than 600 volts. The large rating transformer is earthed through the neutral grounding resistor (NGR) to limit the fault current to its full load current.
The value of the NGR is ;
R= (Vph/√3)*If
Where,
Vph – Phase Voltage
If – Full load Current of equipment.
A current transformer (CT) may be connected between the neutral and the earth point, and the unbalanced current flowing through the CT can be fed to a protective relay for necessary circuit protection.
Equipment Grounding:
The process of connecting the frame or enclosure of electrical equipment to the ground point is called equipment grounding, which is synonymous with equipment earthing.
Neutral
Neutral serves as a return path for electric current, thus completing the electrical circuit. In a single-phase circuit, the phase current flows through the neutral to complete its path. As a result, the phase current and the neutral current are equal in this type of circuit.
In a 3-phase, 4-wire electrical system, the neutral current flows through the neutral only when the loads connected to the three phases are not balanced. When the loads are balanced, no current flows through the neutral, and current through the neutral to the grounding point is absent. You may have noticed that the neutral point is absent in the stator of an induction motor, which is connected to three phases. This is because the motor is a balanced load, and there is no possibility of current flow through a neutral conductor.
The phase current becomes unbalanced during a fault condition, causing the unbalanced current to flow through the neutral. The neutral point is grounded to divert fault current and protect equipment from abnormal current.
Difference between Grounding and Neutral
After understanding the idea of grounding and neutral, we can say that a neutral wire acts as a return pathway for AC, while the ground functions as a low-impedance pathway for “grounding” fault current. The neutral carries both normal and fault current, while the ground carries only fault current.
Earthing:
The electrical devices are housed in a panel called enclosure. The panel is an isolated enclosure that provides necessary insulation between the live parts and the enclosure. If the insulation fails or any conductor gets disconnected and touched by the enclosure body, the enclosure body will attain the live potential.
If a person touches the enclosure, he may get an electric shock. The enclosure is connected to the earth’s potential to protect the man and machine so that the current will be passed to the ground. In this case, the current’s magnitude will be very high, and it will trip the circuit breaker or blow out the fuses.
The electrical panels, motors, generators, transformers, and all the electrical equipment must be earthed from two different points on the equipment body through the two distinct earth pits.
Importance of Earthing:
The earthing is done to eliminate the possibility of electrocution if a human being accidentally touches the live parts. The earthing also protects the equipment. The earthing provides the least impedance path to the fault current. The three terms related to earthing are as follows.
1. Grounding
2. Earthing
3. Bonding
Difference between Grounding and Earthing
The difference between grounding and earthing is summarized in the table below.
| Earthing | Grounding |
| Earthing Point has zero potential. | If the current is balanced in all three phases, the grounding point has zero potential; otherwise, the neutral point has some potential. |
| The earth wire used is green in color. | The ground wire is black in color. |
| Earthing is done to prevent an electric shock to humans when live parts touch the enclosure body and the person touches the enclosure at the same time. | Grounding potential rises from zero to phase voltage when a fault occurs in the system. The grounding allows the flow of large currents from live potential to earth, and the protection relay senses the fault current and trips the upstream breaker and, thus, safeguards the human and machine. |
| The non-live parts of the electric enclosure are connected to earth point. | The neutral point( the live part of supply has zero potential under normal conditions) is connected to the earth’s potential. |
Bonding:
The metallic items that are not designed to carry electricity in the room or building are intentionally connected to the earth to avoid the possibility of electric shock. The process is known as bonding. All the equipment connected will be at the same potential, and if someone touches two pieces of equipment simultaneously will not get an electric shock because no current flows if the potential difference is zero.
If the phase conductor touches the metal part, the equipment will get the electrical potential. This will cause a large current to flow through the bonded piece of equipment to the ground, and the circuit breaker will get tripped.
Conclusion:
The earthing and grounding are very important for the safety of the equipment and persons. The neutral connected to the earthing point is called the grounding, and the equipment enclosure connected to the earth is called equipment earthing or equipment grounding.
