Ever seen an Electric motor from inside ?
There is very minor air gap in between stator & rotor. Power transfers from stator to rotor takes place through air.
Even due to air gap, rotor rotates with so much power. The Principle behind that transformation is known as “Faraday law of Electromagnetic Induction“.
Which means Electrical power can transferred through an air in a form of electromagnetic field. Electrical appliances with metallic body always remains in danger of potential generation even in normal working conditions due to induction,
Apart from that, There are always risk of potential appearance in fault scenario.
Potential generation on a metallic body occurs for various reasons. It is very dangerous for humans and machines, That should be eliminated. Machines metallic surface should also be potential free at any cost.
Introduction
0 Volts or potential free surface can be achieved by connecting the Electrical machine with an Earthing. Proper Earthing guarantee the safety !
Improper Earthing is one of the most ignored electrical safety issues in homes and industries. Many people believe Earthing is only required to protect appliances. In reality, it plays a critical role in saving human life.
In this article, we’ll explain :
Earthing
” Earthing is a type of potential free safety conductor. “
Earthing is been obtained by digging the conductor such as a copper deep down in Earth. Electrically conductive material is been poured around that conductor in between the soil to minimize the overall soil resistance.
Earthing is a zero node. It keeps exposed metal parts at zero potential. When any type of potential appear on Earthing, It diverts the current towards the Earth.
A GIF below shows the working of Earthing. In this, It is been seen that antenna on above the house is connected to Earthing. When lightning fall on that antenna, Current get towards towards the Earthing.
What that means earthing is not proper ?
Earthing diverts or spread the leakage current on soil deep down in Earth. We can say, Earthing is a type of sink which absorbs the leakage current. Higher the current it absorbs, Better the earthing quality.
Resistance is a type of opposition offered by a material to the flow of electrical current. Resistance is measured in numerical value through the units ‘Ohm‘.
1 ohm Resistance is an opposition to the flow of 1 Amps current under the pressure of 1 Volts.
The quality of Earthing depend upon its overall resistance value around the soil. Lower the resistance value, higher or greater the quality of Earthing.
Ideally Earthing has a value of 0 ohm. But Earthing below than 1 ohm is considered as an excellent Earthing.
Earthing Resistance Standard
There is no fixed standard for Earthing resistance . But as we know, Lower the resistance better the earthing will be.
As per IEC 62305 Protection against lightning , 10 Ohms are the highest value required for lightning protection systems
As per 80-2013 – IEEE Guide for Safety in AC Substation Grounding , 0.5 to 1 ohm is the value required in substations .
How to Check If Earthing Is Proper
Earthing is checked through 3 parameters such as resistance , Voltage & current. Three Earthing testing methods are :
- Earthing resistance
- Voltage between neutral & earthing
- Earth ground clamp
1. Earthing resistance
In this method, Soil resistance around the soil is been measured. Metallic electrodes been digged on Earth at fixed distances.
A known current is been applied at Earth electrode & one of the outer test electrode. A voltage is been measure in between Earthing electrode & inner test electrode.
Through Voltage & ampere values, soil resistance is been calculated. This method of earthing testing is known as “fall of potential method”.
A GIF below shows the working procedure of fall of potential method. In this procedure there are 2 stakes in along with earthing that are inner stake & outer stake. Both the stakes are placed at equal distances.
When a test button is pressed, A known current flows from Earthing electrode & outer stake. In that mean time, Voltage is been measured through inner stakes. Through both the values voltage & current, Resistance is calculated. (V=IR)
2. Voltage between neutral & Earthing
In this method, With the help of multi-meter or volt-meter, An AC voltage is been measured in between neutral & Earthing.
Earthing is a type of zero node. The working node should always stay at 0 V. Neutral is a type of return path towards the source. Ideally neutral also stays at 0 Volts. But in real circumstances, Neutral can gain some potential residue of AC voltage specially when neutral wire/cable length is long.
Voltage between working Earthing & neutral should always be less than 2 Volts. “
3. Earthing ground clamp
Clamp type Earthing tester are special devices made for Earthing measurement. In this method, A known voltage is been generated by this meter around the testing Earthing. While a current is measured through the clamp of the device.
With the help of voltage & current, Resistance value is been calculated.
Signs of Improper Earthing
- Mild shock when touching appliances
- Frequent MCB tripping
- Burning smell near sockets
- Bulb glowing dim or flickering
What if Earthing is not connected ? consequences !
Safety is the top most priority Which can not be neglected. And Earthing guarantee the safety !
If Earthing is connected, consequences can be dangerous. Next, some of the consequences are discussed .
⚠️ 1️. Danger of Electrical shock
- Chances of potential generation on metallic surface get enhanced greatly.
- Even we do not dare to touch an electrical appliance as there is no guarantee of safety.
⚠️ 2. Neutral Imbalance
Distribution Transformers contains neutral. Neutral is type of return path Which is been made through the mid point of Start winding configuration.
Neutral stays balanced only when load across all the three phases is balanced. Equal loads on all the 3 phases.
In real circumstances, it is very difficult to balance the load on three phases. This results in potential appearing on the Neutral terminal. This can be eliminated by connecting the Earthing to Neutral .
⚠️ 3. Surge/lightning arresters do not work
Surge/lightning arrester work either diverting or blocking the high voltage spikes. Diverting or blocking is only possible with the help of Earthing.
A GIF shown below shows the working of Surge arrester. Arrester is connected with phase & neutral in parallel with the load. When surge appear across the line, It diverts the high voltage spike towards the Earthing.
⚠️ 4. Malfunctioning in sensitive system & Equipments
Some sensitivity devices or instruments which are working on milli volts can easily get disturbed due to potential generation.
Potential appearance on sensitive electrical loads can produce malfunctioning in system. Such as load cells in weighing scales. That cells working on milli volts, A little variation can produce a big variation.
⚠️ 5. Power quality issue (get deteriorates)
- Noise in supply such as harmonics & distortion
- Malfunctioning due to poor power quality
⚠️ 6. Legal & Insurance issue
- Electrical inspection failure
- Insurance claim rejection after fire accidents
- Warranty claims often rejected due to poor earthing
SUMMARY
- The article discusses the importance of earthing in electrical systems to ensure safety against electrical shocks and other hazards.
- It explains how earthing functions as a potential-free safety conductor by directing leakage currents into the ground. The quality of earthing is contingent upon its resistance, with lower values indicating better quality.
- Improper earthing can lead to dangers such as electrical shocks, distribution transformer inefficiencies, malfunctioning of sensitive equipment, and legal liabilities.
- The piece emphasizes that proper earthing is critical for both appliance protection and safeguarding human life, outlining methods for testing earthing effectiveness.
FAQs
Q1. Can RCCB work without Earthing?
Partially, but effectiveness reduces significantly.
Q2. What is ideal Earthing resistance value?
Generally below 1 ohm for domestic installations.
Q3. Is earthing mandatory for homes?
Yes, as per electrical safety standards.
Q4. Why do I feel shock even with MCB installed?
MCB protects against overload, not leakage. Earthing + RCCB are required.