Earthing means to connect electrical system to earth or soil in such a manner as it ensures an immediate discharge of electrical energy without any danger. It is the most essential part of electric work which must be provided to protect from any mishap. It saves human life from sudden electric shock. When proper earthing is done in building, it saves building of thunder effects i.e. from fall of natural cloud lighting.
Purpose of earthing:
- To save human life from danger of electric shock or death.
- To protect building, machinery and appliances under fault condition.
- To ensure that all exposed conductive parts do not reach a dangerous potential.
- To provide safe path to dissipate lighting and short circuit currents.
- To maintain the line voltage constant to prevent over current or excessive voltage on the appliances or equipments.
In general earthing is not provided in building at the time of electrical fittings either due to ignorance/carelessness or to save expense on earthing.
How to do earthing:
The following is the method of implementation of earthing:
- The size of the earth pit should normally be 1500 mm X 1500 mm X 3000 mm.
- Low earth resistance is required to give effective earthing protection to electrical fittings.
- Dry earth has more resistance whereas moist earth has less resistance.
- The location of earth pit should be such where the soil has reasonable chances of having moisture. If possible earth plates or pipes should be located near water tap, water drain or rain water pipe.
- Electric earthing may be either pipe or plate earthing.
- Normally GI pipe (2.5 inch diameter) or plate (500 mm X 500 mm X 10 mm) is used but if the soil is corrosive then copper pipe or plate should be used.
- Use Double GI Strip size 30 mm X 10 mm to connect GI Plate to System Earthing.
- A mixture of Wood Charcoal Powder, Salt and Sand, all in equal part, must be filled in the earth pit around earthing pipe or plate. The purpose of coal and salt is to keep wet the soil permanently.
- The position of the earth plate or pipe when fixed should be clear from all building foundations.
- A masonry enclosure should be made over earth pit.
- Entrance, pavement and roads should be avoided for locating earth pit.
- Inside building in addition to all electrical appliances, all switch boxes, meter boxes etc. should be earthed also.