Electricity is one of the most used things by humans. It is transported from the powerhouse through the wires to the various houses and industrial locations. Electric current has two main types - Direct current and Alternating current. Alternating current mainly flows in the wires which see around us.
Electricity has given new dimensions to power systems and technology, however, it can be dangerous also. Spark in electrical wires can lead to a fire. If touched directly, live wires can also give shocks. Keeping these things in mind, for the safety of humans and the powerhouses we used several techniques to minimize these damages. Earthing and ground are methods to prevent any such incidents.
Often, we think they both are the same things but actually, they have many differences. These days most power systems use these safety measures according to international standards. In the next sections, we shall study these in detail.
It is a safety measure against the unwarranted fluctuations of electricity that can lead to damage to life and property. In this method, the electric circuit is physically conceded to the ground. The wires these days have three components mostly. Live wire, Neutral wire, and the Earth wire. In earthing the Earth wire is connected to the ground.
If somebody touches the wire or any device which has current by mistake then he may get shocked. But this earthing wire discharge the current towards the earth. Earthing also safe our appliances from the lighting, any extra charge will be passed to the earth.
Usually, the earthing system is placed below the ground in soil.
Earthing in a circuit is depicted by the following symbol -
Fig:1 symbol of earthing
Mainly there can be Five types of earth
Pipe Earthing - In this type, A pipe is grounded in the earth.
Plate Earthing - In this type, A copper plate is placed inside the earth, it is considered one of the best kinds of earth.
Strip Earthing - It is done for transmission lines. The rocky ground is necessary for this kind of the earth.
Coil Earthing - It is used in very small quantities. Galvanized Iron wire is used in this.
Rod Earthing - It is used in areas where moisture is very high. In sandy areas, the earth is dug deep and used as a pipe in this kind of the earth.
It is similar to the earthing process, however, there are certain differences. In this process, the current-carrying part of the circuit is connected to the ground. The live wire of the circuit is connected to the supply and the neutral wire is connected to the earth. Electric equipment is grounded in a manner that the voltage difference between the ground and device will be zero. It saves the devices such as transformers, and generators from faults. Since during the fault, the phases become unbalanced and the grounding provides a passage to extra current.
Similar to the earthing the grounding also has a symbol in a circuit. It is denoted by the following
Fig:2 Symbol of grounding
The main types of grounding are the following -
Solid grounding system - It is very useful in industrial power systems. In sold grounding system the neutral wire is connected to the ground. This system easily locates the faults.
Resistance grounding - It has two types - High resistance grounding and low resistance grounding. In high resistance grounding a high resistance is placed between the ground and the neutral point of the low voltage transformer.
In Low resistance grounding, the small resistor is connected between conductor and ground. It is used as a Load.
Reactance grounding - In this type of grounding, a reactor is used between the ground and the neutral point. These days it is not used very much since it is not useful during ground faults.
Resonant grounding - A coil is used in this kind of grounding. The coil is connected to an underground three-phase system. The coil is connected with each phase ground in a series connection. It is based on the LC circuit and is also known as Peterson grounding.
| Earthing | Grounding |
|---|---|
| Is used as safety against electric shock. | Mainly used for the safety of appliances |
Used when there is a need for electric discharge. | Used when there is electric imbalance due to overloading in the system |
It protects from lighting | It is used in reducing the frequency of faults. |
Used in homes, motors, and generators. | Used in power transformers and neutral motors |
Earthing and grounding are used as safety measures in electrical circuits and devices. They have many similarities and differences between them. In the process of earthing the, in the electrical circuit, the earthing wire is used. But in grounding the neutral wire of the electrical circuit is used. The grounding has four types and earthing could be of five types. These are commonly used in generators, motors, transformers, and other electrical devices.
Q1. What is the electric potential difference?
Ans: We can define the potential difference between two points in the following way. Suppose there are two-point A and B in an electric field, then the work done in moving the charge from A to B is called the potential difference between them.
It is given by
$$\mathrm{V_{AB}=\frac{1}{4\pi \epsilon_0} \frac{q}{r_A-r_B}}$$
Q2. Can we take the potential of earth zero? How?
Ans: Yes, for practical uses we can take it to zero. We know that at the infinite distance the potential is zero. The potential at the surface of the earth is given by -
$$\mathrm{V=\frac{q}{4\pi \epsilon_0 r} }$$
Since the radius of earth r is too large in comparison to the movement of charge. We can take this value r to infinite. And hence the potential will be zero.
Q3. How does the earthing saves from lighting?
Ans: The current flows to such a path quickly where the resistance is low. The earthing provides the lighting a low resistance alternate path. And the whole charge is transferred to earth.
Q4. Discuss the resistance of the earthing?
Ans: For easy electric discharge, the resistance of the earthing should be very low. The ideal resistance is zero, but it is not possible to achieve. Earthing resistance has a different value for different purposes. For example - for homes, it is around 8Ohm and for power plants, it is around 0.5Ohm.
Earthing resistance can be reduced in the following ways-
By maintaining the moisture of earth
By increasing the contact area and depth of the electrodes
By using the salt where the electrode is placed inside the earth
Q5. What are the differences between earthing and grounding?
Ans:
| Earthing | Grounding |
|---|---|
Saves from shock | Saves from malfunctions of devices |
Have zero potential | Need not to have zero potential |
Placed between the device and earth | Placed between neutral of device and ground. |
Have Five types | Have four types |
The green wire is used | The Black wire is used |
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