Earthing and its types

The process in which the instantaneous discharge of the electrical energy takes place by transferring charges directly to the earth at zero potential through low resistance wire is called earthing.

Objective of Earthing:

  1. T overcome dangerous electric shock exposed to the person working area.
  2. To provide current carrying capacity both in magnitude and duration which is sufficient to accept the ground fault current permitted by overcurrent protective system without creating a fire or explosive hazard to the building.
  3. Make the better performance of the electrical system.

Necessity of Earthing:

  1. To provide greater safety to personnel and equipment from the danger of leakage current.
  2. To maintain constant voltage in a healthy system.
  3. To protect equipment and building from lighting.
  4. To serve as a return conductor in communication and traction work.
  5. To protect all machinery feed from OH lines from lightning.

Types of Earthing:

1. Pipe Earthing:
  1. It is common and best system of earthing with compared to other types under same environmental status.
  2. Here galvanized steel pipe of suitable dimension place in a permanently wet soil.
  3. The diameter of pipe is 40 mm and length is 2.5 meters. (Length can be increase according to the condition of soil).
  4. The depth of pipe buried to ground is depends on the condition of moisture in soil.
  5. Lower side of pipe is surrounded by charcoal and salt (NaCl) at length upto 15 cm by means of alternate layer.
  6. Another pipe of 19 mm diameter and minimum length 1.25 meters is connected at the top of GI pipe through reducing socket.
  7. Cement concrete box work is done for bucketing of water.
  8. It is used for ordinary soil or dry and rocky soil.
2. Plate Earthing:
  1. Either copper (60 cm × 60 cm × 3 m) or GI (60 cm × 60 cm × 6m) is used as a plate is buried into the ground with its face vertical upto 3 m depth.
  2. Charcoal and salt (NaCl) at length upto 15 cm by means of alternate layer.
  3. The earth wire is tightly bolted to an earth plate with the help of nut or bolt.
  4. It is used for larger stations and transmission lines, where the fault current, is likely to be high.
3. Rod Earthing:
  1. Rods used as Earth Electrode.
  2. It buried directly in the ground, facilitating the flow of fault currents towards the ground.
  3. This system of earthing is suitable for areas that are sandy in character.
  4. It is also known as fire earthing.
  5. This system of earthing is very cheap as no excavation work is involved.
4. Strip Earthing:
  1. Either copper strip of (25 mm ×1.6 mm) or GI strip of (25 mm × 4 mm) is used.
  2. It buried to ground in horizontal trenches of a minimum depth of 0.5 m.
  3. Strip earthing is used in transmission processes and in places that have rocky earth beds

Equipment Earthing

https://www.electricalje.com/2023/03/equipment-earthing.html

Top MCQs questions on Earthing for SSC JE Electrical:

Question: Induced low voltage on metal equipment, which causes a low shock, can be prevented using:
A) Phase line earthing
B) Neutral
C) Insulated footwear
D) Clothing
Answer: B) Neutral
Explanation: The main function of the earth wire (neutral) is to prevent the live wire from overloading and absorb excess electrons, allowing them to flow to the ground. Earthing is necessary to protect against electric shock, high voltage surges, and lightning discharge.
Question: How can the pipe earthing resistance be regulated?
A) Replacing the conductor
B) Adding a copper rod
C) Adding salt and water
D) Replacing the earthing rod
Answer: C) Adding salt and water
Explanation: In pipe earthing, adding salt and water helps regulate the resistance. The galvanized steel and perforated pipe are buried in permanently wet soil. Alternate layers of coke and salt increase the effective area of the earth and decrease resistance.
Question: Which electrode is used for pipe earthing?
A) Copper rod
B) Steel rod
C) Galvanized iron (GI) pipe
D) Aluminum rod
Answer: C) Galvanized iron (GI) pipe
Explanation: The pipe earthing method involves using a galvanized steel and perforated pipe of approved length and diameter buried upright in permanently wet soil. The pipe’s bottom is surrounded by coke and salt layers to enhance conductivity.
Question: For the measurement of the earth resistance of a given earth electrode, what should the collecting electrode be?
A) Very near to the electrode under test
B) Touching the electrode under test
C) Far away from the electrode under test
D) None of the above
Answer: A) Very near to the electrode under test
Explanation: The collecting electrode should be very near to the electrode under test for accurate measurement of earth resistance.
Question: What is the purpose of earthing in electrical systems?
A) To reduce energy consumption
B) To prevent overloading of live wires
C) To improve power factor
D) To enhance voltage stability
Answer: B) To prevent overloading of live wires
Explanation: Earthing protects against electric shock, overloading, and lightning discharge.
Question: Which type of soil is suitable for pipe earthing?
A) Dry and rocky soil
B) Sandy soil
C) Moist soil
D) Clayey soil
Answer: C) Moist soil
Explanation: Pipe earthing works best in moist soil conditions.
Question: What is the purpose of adding salt and water in pipe earthing?
A) To increase resistance
B) To decrease resistance
C) To prevent corrosion
D) To improve conductivity
Answer: D) To improve conductivity
Explanation: Adding salt and water enhances the effective area of the earth and decreases resistance.
Question: Which material is commonly used for pipe earthing?
A) Aluminum
B) Copper
C) Galvanized iron (GI)
D) Stainless steel
Answer: C) Galvanized iron (GI)
Explanation: GI pipes are commonly used for pipe earthing.
Question: What is the depth at which the pipe must be buried for pipe earthing?
A) 1 meter
B) 2 meters
C) 3 meters
D) 4 meters
Answer: C) 3 meters
Explanation: The pipe is placed at a depth of 3.75 meters for effective pipe earthing.
Question: What surrounds the bottom of the GI pipe in pipe earthing?
A) Sand
B) Charcoal
C) Cement
D) Gravel
Answer: B) Charcoal
Explanation: Small pieces of coke or charcoal surround the bottom of the GI pipe in pipe earthing.
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