Describe with neat sketch any one type of earthing system.
1 Answer
Answer :
Types of Earthing System:
1. Plate earthing
2. Pipe Earthing
3. Strip or wire earthing
4. Rod earthing
i) Plate earthing :
Explanation:
* The earthing is installed as per above figure.
* The size of earthing plate is 60cm x 60cm x 3.18 mm copper.
* The earth wire having the size of 8 gauge copper, the earthing plate is surrounded by the alternate layer of charcoal and salt.
* To minimize the earth resistance the earthing maintenance is required, to maintain this earth resistance the pouring of salt water in the wire mesh by removing the cover on wire mesh for every month.
* The Plate type earthing is generally carried out muddy area where percentage of loose earth soil is more
ii) Pipe Type earthing:
* This earthing is generally carried out in locky area where digging is not possible.
* In that case by boaring the suitable diameter of hole in locky area at the depth of 3.75m.
* The earthing GI pipe having the diameter of 38 mm are embedded in the ground with alternate layers of charcoal and salt.
* 8 Gauge copper wire is also taken outside in addition with 10 mm diameter GI pipe.
* The wire mesh is necessary by pouring the salt in the earthing pit.
OR
* Excavation on earth for a normal earth Pit size is 2.7 M X 0.6 M X 3.0 M.Or 4.5 M
* For Pipe type earthing normal practice is to use; GI pipe [C-class] of 75 mm diameter of length Having 6 numbers of holes for the connection of earth wires
* Normal Practice is to use GI earthing pipe of length.
* Cover Top of GI pipe with a T joint to avoid jamming of pipe with dust & mud and also use water time to time through this pipe to bottom of earth plate when required.
* These types of earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the bottom of the pit.
* Make a mixture of Coal Powder, Salt & Sand all in equal part.
* Use of Coal Powder also beneficial as it is anti-corrosive.
* The electrical installation which to be earthed, is connected to the top of the earth rod by means of copper or aluminium earth continuity conductor of sufficient cross-section.
iii) Strip type or wire type earthing:
* In this type or earthing the copper strip which are more than one, are connected in parallel with each other and separated at least 30 cm from each other.
* The copper strip which are connected in parallel are surrounded by the alternate layers of charcoal and salt.
* The 8 gauge copper wire, which is connected to the brass nutbolt to the earthing strip is taken outside as a earth wire.
* For the maintenance of earth resistance, the pouring of salt water is done by through the wire mesh.
* The strip type earthing is generally done in rocky area soil condition.
iv) Rod type earthing:
* This is cheapest and easiest method of earthing as this method does not require any excavation work.
* In this type of earthing, a metallic rod of sufficient length is driven vertically into the ground normally by hammering on the top.
* The driven rods be a minimum of 8- 10 feet in length and length of rod must be in direct contact with the soil.
* The electrical installation which to be earthed, is connected to the top of the earth rod by means of copper or aluminium earth continuity conductor of sufficient cross-section.
* Rod type earthing is generally used for muddy area or rocky area for immediate earthing purpose.