Electric Shock and Earthing: Types of Earthing

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Earthing is a basic method for preventing current leakage and thereby protecting equipment from electrical damage. Grounding is another safety procedure that protects the entire power system from failure and is mostly used to balance the load when the electric system overloads.

When a significant amount of the electric current passes through the parts of the human body there will be a disturbance and excitation of the function of nerves or muscles, termed as electric shock. A sudden discharge of electricity through the human body is also termed an electric shock. A person occurs an electric shock when he/she came in contact with an electrical energy source. When an electric current flows through any physical body or any object they absorb the energy and when the amount of absorbed energy is high, affects the body.

Electric Shock and Earthing
Electric Shock and Earthing

Mainly, the organs affected when the current flows through the human body are the respiratory and heart organs. Many people get electrical shocks from different electrical appliances, electrical circuitry, and electrical wires. Whenever the electric current starts flowing through the different parts of the human body, such as organs, tissues, and systems, there is an absorption of electric energy. The nature of observed energy depends upon the parts of the human body through which the current flows and the entry of electric current into the body. Self-control becomes fully disturbed, and the heart stops functioning. This is the primary symptom.

pic sources: Electric shock | definition of electric shock by Medical dictionary

There will be pain at the point of entry and exit of current when a significant amount of current is through the body. Contraction of the muscles resulting spasm muscle pain and torn muscles and ligaments. a person becomes fully enable to take self-protective action due to loss of muscle control. contraction of chest muscles, diaphragm, and throat results in breathing problems. And at last cause Ventricular fibrillation.

Ventricular fibrillation is a case whereby the heart ceases to contract and random twitching of the nervous muscular fibrils occurs. Fibrillation of the heart means cessation of the heart activity, interruption in the functions of the heart and death occurs because of the lack of oxygen.

pic source: Virtual Labs

  • move the victim to a safe place but don`t endanger yourself/
  • De-energizing the electric equipment from the supply switch.
  • Cutting cable or wire to apparatus using a wooden -handle axe.
  • Protect your eyes against flash.
  • Use an electrical nonconductor such as a dry stick, dry rope, leather belt, coat, or blanket to move the victim away from the contact.
  • Ascertain whether the patient is breathing or not. If breathing, Then, keep the patient in a reclining comfortable position and loosen all clothing around the neck, chest, and abdomen.
  • If the victim is not breathing utilize the Cardiopulmonary resuscitation (CPR).
  • If the heart has ceased beating have first aid immediately with a qualified person.

Safety Precautions and Regulations

The best method for protection against electric shock is insulation. Insulation of the conductor and insulation of the worker provide protection against electric shock. Some of the different safety precautions and regulations for electric shock are:

  1. Always switch off the mains switch before replacing a blown fuse.
  2. Always use the correct size of fuse, while replacing blown fuse.
  3. Safety depends upon good earthing.
  4. Be aware of live wires or conductors bare or insulated.
  5. Before the replacement of any electrical requirements be sure that the switch  is OFF.
  6. Be sure that all the connections are tight.
  7. If you are working on the inductive circuit or cable discharges them.
  8. Put the safety belt when you are working above the ground level or pole.
  9. Never disconnect a plug point by pulling the flexible wires.
  10. Never temper unnecessarily with any electrical apparatus.
  11. Never touch an overhead line unless you are sure that it is dead and properly earthed.
  12. Never energized a line unless you are sure that all is clear and no one is working.
  13. while working on the motor /Generator make sure that no one can put it in position without your permission.
  14. Never bring a naked light near the battery when it is in a charged state and maintain good ventilation.
  15. Must use the rubber mats near the electrical panels and switchboard.

Earthing and shielding Techniques for Personnel and Equipment Protection

What is Grounding or Earthing?

Earthing or grounding is the connection of metallic parts of an electrical appliance, electrical machinery, and devices to the earth plate or earth electrode through a thick conductor wire.

Earthing is the connection of the neutral point of a power supply system to the earth so as to avoid or minimize danger during the discharge of electrical energy.

Need of Earthing or Grounding. Why Earthing is Important?

The primary purpose of earthing is to

  • avoid or minimize the danger of electrocution fire
  • and ensure that the potential of a current-carrying conductor does not rise with respect to the earth than its designed insulation.

When the metallic part of electrical appliances (parts that can conduct or allow passage of electric current) comes in contact with a live wire, maybe due to failure of installations or failure in cable insulation, the metal become charged and static charge accumulates on it. If a person touches such a charged metal, the result is a severe shock.

Needs of Earthing

To protect human lives as well as provide safety to electrical devices and appliances from leakage current.
 To keep the voltage constant in the healthy phase (If the fault occurs on any one phase).
 To Protect Electric systems and buildings from lighting.
 To serve as a return conductor in electric traction systems and communication.
 To avoid the risk of fire in electrical installation systems.

Methods of Earthing | Types of Earthing

Earthing can be done in many ways. The various methods are discussed as follows:

Plate Earthing

In plate earthing system, a plate made up of either copper with dimensions 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in) or galvanized iron (GI) of dimensions 60cm x60cm x 6.35 mm (2ft x 2ft x 1⁄4 in) is buried vertical in the earth (earth pit) which should not be less than 3m (10ft) from the ground level. For a proper earthing system, follow the
above-mentioned steps in the (Earth Plate introduction) to maintain the moisture condition around the Earth electrode or Earth plate.

Pipe Earthing

A galvanized steel and a perforated pipe of approved length and diameter is placed vertically in wet soil in this kind of system of earthing. It is the most common system of earthing. The size of pipe to use depends on the magnitude of the current and the type of soil. The dimension of the pipe is usually 40mm (1.5in) in diameter and 2.75m (9ft) in length for ordinary soil or greater for dry and rocky soil. The moisture of the soil will determine the length of the pipe to be buried but usually, it should be 4.75m (15.5ft).

Rod Earthing

It is the same method as pipe earthing. A copper rod of 12.5mm (1/2 inch) diameter or 16mm (0.6in) diameter of galvanized steel or hollow section 25mm (1inch) of GI pipe of length above 2.5m (8.2 ft) is buried upright in the earth manually or with the help of a pneumatic hammer. The length of embedded electrodes in the soil reduces the earth’s resistance to a desired value.

Strip or Wire Earthing

In this method of earthing, strip electrodes of cross-sections not less than 25mm x 1.6mm (1in x 0.06in) are buried in a horizontal trench of a minimum depth of 0.5m. If copper with a cross-section of 25mm x 4mm (1in x 0.15in) is used and a dimension of 3.0mm2 if it’s a galvanized iron or steel. If all-round conductors are used, their cross-section area should not be too small, say less than 6.0mm2, if it’s a galvanized iron or steel. The length of the conductor buried in the ground would give a sufficient earth resistance and this length should not be less than 15m.

References

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