The Methods of Earthing classify and explain below
1. Earthing Mat
2. Earthing Electrode
3. Pipe Earthing
4. Plate Earthing
5. Earthing Through Water Mains
An earthing mat is a system of interconnected conductive rods that is installed in the ground to provide a low resistance path for fault currents to flow to earth. When an electrical fault occurs, such as a short circuit or a ground fault, the fault current will flow through the earthing mat and into the ground, rather than through a person who may be touching a non-current-carrying surface of the electrical system. This helps to protect people from the potentially dangerous voltage that can be present in a fault condition.
The design of an earthing mat takes into consideration several factors to ensure that it is effective in limiting the ground potential and protecting people from electrical hazards. These factors include the resistance of the mat, the fault current that may flow through it, and the step voltage between the ground and the ground surface.
To minimize the resistance of the earthing mat, it is important to use conductive materials such as copper or aluminum and to ensure that the mat is connected to the ground in as many places as possible. The fault current that may flow through the mat should be large enough to operate the protective relay, which is a device that automatically shuts off the electrical power in the event of a fault. The resistance of the mat should also be low enough to allow the fault current to flow through it, but not so low as to permit the flow of fatal current through a person's body.
2. Earthing Electrode:
An earthing electrode is a conductive element that is installed in the ground to provide a low resistance path for electrical fault currents to flow to earth. There are many different types of earthing electrodes, including rods, pipes, plates, and bundles of conductors. These electrodes can be installed horizontally or vertically in the ground, depending on the specific requirements of the electrical system.
In distributing systems, such as those used to distribute electricity from a power plant to homes and businesses, the earthing electrode may consist of a single rod that is driven vertically into the ground. The rod is typically about one meter in length and is made of a conductive material such as copper or aluminum. The rod is connected to the electrical system through a conductor, which carries fault currents to the rod in the event of a fault.
In generating substations, which are facilities that generate, transform, and distribute electrical power, a grounding mat is often used instead of individual earthing rods. A grounding mat is a large network of interconnected conductors that is installed in the ground to provide a low resistance path for fault currents. The mat is typically made of copper or aluminum and is connected to the electrical system through a conductor. The use of a grounding mat in a generating substation allows for the rapid dissipation of fault currents, helping to protect the electrical system and the people who work in the substation.
Finally, the design of the earthing mat should aim to minimize the step voltage between the ground and the ground surface. This is important because the step voltage can be dangerous to a person who is touching the ground, and it is influenced by the resistivity of the soil and the fault current required to isolate the faulty plant from the live electrical system. By carefully considering these factors, an earthing mat can be designed to effectively protect people from electrical hazards and limit the ground potential in a fault condition.
3. Pipe Earthing:
Pipe earthing is a system of earthing in which a galvanized steel pipe is installed upright in the ground to provide a low resistance path for electrical fault currents to flow to earth. This type of earthing is commonly used because it is effective in a wide range of soil and moisture conditions.
The size of the pipe used for earthing depends on the current that needs to be carried and the type of soil. A pipe with a diameter of 40 mm and a length of 2.5 meters is typically used for ordinary soil. For dry or rocky soil, a longer pipe may be needed. The depth at which the pipe is buried also depends on the moisture content of the soil.
To further improve the effectiveness of the earthing system, the bottom of the pipe is surrounded by small pieces of coke or charcoal, and alternate layers of coke and salt are used. These materials help to increase the effective area of the earth and decrease the earth resistance, respectively.
A smaller diameter pipe, typically 19 mm, is also connected to the top of the main pipe through a reducing socket. This smaller pipe is used to provide access to water, which can be poured into the pipe through a funnel during summer to maintain the moisture content of the soil and keep the earth resistance low.
Finally, an earth wire, which is a conductor used to carry fault currents safely to the earthing system, is typically run through a separate pipe of diameter 12 mm at a depth of about 60 cm from the ground. This helps to protect the earth wire from damage and ensure that it is able to effectively carry the fault currents to the earthing system.
4. Plate Earthing:
In plate earthing, an earthing plate is buried in the ground to provide a low resistance path for electrical fault currents to flow to earth. The earthing plate can be made of copper or galvanized iron, and is typically rectangular in shape with dimensions of 60 cm by 60 cm. For a copper plate, the thickness is typically 3 mm, while for a galvanized iron plate it is typically 6 mm.
The earthing plate is buried in the ground with its face vertical at a depth of not less than 3 meters from ground level. This is to ensure that the plate is deep enough to provide effective grounding, while still being accessible for maintenance and repair.
To further improve the effectiveness of the earthing system, the earthing plate is often surrounded by auxiliary layers of coke and salt. These materials help to increase the effective area of the earth and decrease the earth resistance, respectively. The thickness of the auxiliary layers is typically at least 15 cm.
An earth wire, which is a conductor used to carry fault currents safely to the earthing system, is tightly bolted to the earthing plate using a nut or bolt. The earth wire can be made of galvanized iron or copper, although copper is typically more expensive and is not used as often for grounding purposes.
5. Earthing Through Water Mains:
In this type of earthing, an earth wire made of galvanized iron or copper is connected to a water main using a steel binding wire. The water main is a pipe that carries water, and it is typically made of metal. Because the water main is buried below the surface of the ground and is in direct contact with earth, it serves as an effective conductor for electrical fault currents.
To connect the earth wire to the water main, the steel binding wire is used to fix the copper lead to the water main. The copper lead is a short length of copper wire that is used to make the connection between the earth wire and the water main.
When an electrical fault occurs, the fault current will flow through the earth wire and into the water main. Because the water main is in direct contact with the ground, the fault current is able to flow to earth, helping to protect people and equipment from electrical hazards.