The main reason for doing earthing in the electrical network is for the safety. Earth or ground wire is mainly to protect the human from electrical shock. If there is contact between live wire directly to metal case/body of the application or device, the user shall get a shock because the current will flow towards the earth through the user body if that person is in contact with the earth. The green earth wire is attached to the metallic body/case of the appliance/device and allows the current to go directly to the earth without harming the user. This earth cable is finally attached to an earthing electrode as shown in the image below.
The electrode is buried mostly in the moist conductive soil through a thick conductor wire which should have a very low resistance. This complete arrangement is known as earthing.
PURPOSE OF EARTHING
- Earthing is most important to save human life from the danger of electrical shock or death by blowing a fuse i.e provide an alternate path for the fault current to flow so that it does not harm the user.
- To protect buildings, machinery, and appliances under a fault condition.
- To ensure that all the exposed conductive parts do not reach a dangerous potential.
- To provide a safe path to dissipate lightning and short circuit current.
Factors that can affect performance of earthing –
- #1. SOIL RESISTIVITY is the resistivity of the soil to the passage of electric current. It varies from soil to soil. It depends on the physical composition of the soil, moisture, dissolved salt, grain size, distribution, seasonal variation, current magnitude, etc
- Different soil conditions give different soil resistivity. Most of the soils are very poor conductors of electricity when they are completely dry.
- Soil plays a significant role in determining the performance of the electrode.
- Common salt is most effective in improving the conductivity of the soil. But it erodes metal and hence is discouraged.
- Moisture has a great influence on the resistivity of the soil. The resistivity of the soil can be determined by the quantity of the water held by the soil and the resistivity of the water itself. Conduction of electricity in the soil is through the water.
- Pure water is the poor conductor of electricity. The resistivity of the soil depends on the resistivity of the water which in turn depends on the amount and nature of salt dissolved in it.
- Increase or decrease of moisture content determines the increase or decrease of soil resistivity. More the moisture content less will be the resistivity ( for example in monsoon season )
- The location also attributes to the resistivity to a great extent. In a sloping landscape or hilly areas, water runs off and in dry weather conditions, water table goes down very fast.
- Grain size, its distribution, and closeness of packing are also contributory factors since they control the manner in which the moisture is held in the soil.
Q. What is FLAT-IN-PIPE technology?
The flat-in-pipe concept involves one pipe electrode and a flat electrode. The flat electrode is vertically inserted from top to bottom into the pipe. Inserted flat electrode is either copper coated or zinc coated or pure copper. The empty space between the flat electrode and pipe electrode is filled with a crystalline conductive compound which is highly conductive and anti-corrosive. The crystalline conductive compound does not collapse even if the outer pipe corrodes and thus is no reduction in the earthing surface area even after a long duration.
Over the time this Crystalline Conductive Compound washes out and inner flat electrode comes in direct contact with the soil. Due to an anti-corrosive copper coating of the inner flat, it takes very long time to corrode, which increases the life span of the electrode.
Q. Why copper coating on the inner flat of the electrode is important?
Each and every metal has different resistivity and conductivity. Copper has less resistance and is more conductive compared to iron or steel. The outer copper coating of the earthing electrode plays a vital role in the performance of the earthing system. There is a fact that current flows mostly through the outer surface of the wire or the rod, the phenomenon known as the “SKIN EFFECT”. Copper coating on the inner flat enhances the conductivity due to the skin effect.
When the outer pipe coating corrodes over time, the inner flat electrode comes in direct contact with the earth. Copper coating of the inner flat is more conductive than iron or Gi and hence improves the performance of the electrode. The anti-corrosive property of copper provides more durability and lasts longer than iron or GI.
GROUND CONDUCTIVITY IMPROVING MATERIAL(GCIM)
Earthing system performance mainly depends on the surrounding soil structure and conditions around the earthing pit. The same electrode with same GCIM type and quantity behaves differently as various locations on the earth. Due to this variation in nature or structure of soil, we get different resistance value at various locations with the same earthing electrode.
GCIM is mixed with soil and placed around electrode during the process of earthing installation. When we add GCIM in the soil, the resistivity of the soil will decrease and the conductivity of the soil will increase and hence the overall earth pit performance will be increased. Contents of GCIM are highly conductive and non-corrosive compared to conventional salt and charcoal. Apart from this, water is a good conductor of electricity and water retaining the capacity of GCIM is 600% more than the conventional charcoal. This high conductivity and water retaining the capacity of GCIM improve the overall performance of the earthing electrode.
Difference between CONVENTIONAL EARTHING and MAINTENANCE FREE EARTHING:
Maintenance free advance earthing system is cost effective and long lasting solution.