Earth Leakage Current Cause, Example, Measurement, Protection
Hey, in this article we are going to discuss a very important topic in electrical engineering which is 'Earth Leakage'. We will discuss what is earth leakage current, what are the causes of it, examples of earth leakage, how to measure earth leakage current, and how to prevent or take protection against earth leakage. Earth leakage is a very important factor for electrical installation as it is related to electrical safety also.
What is Earth Leakage Current?
The unwanted, unused, waste current flowing from a live conductor or terminal to the ground or earth through the ground conductor or any other conductive path is called Earth Leakage Current.
In a standard and proper electrical installation, the current should flow through the live conductor, neutral conductor, and load with proper balancing. If any unbalancing happens, then it indicates the leakage current.
Leakage current not only occurs in the electrical installation system, but it may also happen with electrical or electronic equipment, circuits, etc.
Earth leakage current flows through the ground conductor to the earth. If there no grounding or earthing system is available or improper grounding then the earth leakage current will try to flow through any other conductive path i.e., the human body. Although, it is not possible to make an electrical installation with a hundred percent no leakage, but it should not be crossed a limit.
Don't confuse it with earth leakage current and normal leakage current. When the unwanted current flows between live to the ground or earth then it is called earth leakage current. But when an unwanted current flows between two live conductors or live to neutral conductors then it cannot be called earth leakage current.
Example of Earth Leakage
Earth leakage(with a high current) mostly occurs in electrical transmission lines(it can be called earth fault), transformers, and other electrical devices.
Earth leakage(with the medium and low current) occurs with electrical and electronic devices such as washing machines, refrigerators, micro ovens, etc.
Earth leakage(with a very low current) or normal leakage occurs in electronic circuits, PCB boards, mobile chargers, radio-electronic devices, etc.
Causes of Earth Leakage
There are several causes for Earth Leakage.
In an overhead transmission line earth leakage current occurs due to the damaged insulator, broken live conductor, or touching the ground or when the insulator got damaged due to high voltage, over long time use, mechanical damage then, current starts flowing from the live conductor to ground through the pole. Earth leakage may occur in underground transmission lines due to insulation damage of cables. In overhead transmission line earth leakage and line-to-line leakage occurs due to the capacitance effect also.
Earth leakage occurs in electrical machines such as transformers, motors, etc. In these cases, earth leakage mainly happens due to insulation failure, improper connection, etc. Generally, the metallic body of the transformer and motor is always connected to the ground with a grounding conductor. So when earth leakage occurs due to insulation failure of the live conductor, leakage current flows from the transformer or motor body to the ground through the grounding conductor.
In electrical devices such as washing machines and refrigerators, earth leakage happens due to insulation damage, wetness, etc. It should be noted that if any device is not connected to the ground, then there is no chance of earth leakage but it is very dangerous if anyone touches that device.
In electronic circuits, earth leakage or normal leakage current(mostly) occurs due to the capacitance effect. In fact, capacitors used in the electronic circuit for filtering purpose works on the principle of bypassing the noise signal to the ground in the form of leakage current.
Earth leakage current also occurs due to humans. Suppose, by mistake, anyone touches the live conductor standing on the ground then the current will flow from the live conductor to the ground through the body of that person. Of course, that person will get an electrical shock.
Remember that, there are two types of leakage current. In a power supply system, such as a transmission line, earth leakage current occurs in AC form but in the case of equipment, earth leakage current occurs in pulsating DC or AC.
Importance and Effects of Earth Leakage
It is very important and must be considered with proper measurement, and protection systems because it is directly related to human safety from electricity, burning of conductors, fire, etc.
There are many bad effects of earth leakage. For example when earth leakage occurs in the transmission line a huge amount of current flowing to the ground, so it trips the main breaker installed in the substation. So the whole power system will be interrupted which will create economic losses.
The bad effect of earth leakage in electrical devices or equipment is an electrical shock hazard. If the equipment is double insulated or properly grounded there is a low risk of electrical shock. But if the equipment is not properly insulated or not grounded then there is a very big chance of electrical shock when anyone touches the equipment's metal body.
Other effects of earth leakage are,
1. It causes to make the voltage to drop.
2. It causes the flow of excess current in a circuit.
3. It creates electrical power loss.
4. It makes the electrical power system unbalanced.
Earth Leakage Current Measurement
Measurement of the quantity of earth leakage current and identification of the source of leakage current are must required if we want to minimize the effect of earth leakage.
There are different measuring devices and measurement procedures available to measure earth leakage current. A specially designed earth leakage clamp meter can be used to measure earth leakage current. It works on the same principle as a normal clamp meter, just difference is it can measure current in a few milliamperes also, whereas the normal clamp meter fails to measure very low current.
When you put the jaws of a clamp meter around the ground conductor, it will show the leakage current value. But if there is no ground conductor but you think earth leakage occurs through any other conductive path, then also you can measure the leakage current to the ground,
For single-phase, by clamping both phase and neutral conductor together.
For the three-phase, by clamping all three phases and neutral(if available) together. The value showing in the meter will be the earth leakage current.
Protection Against Earth Leakage
As per the electricity rule, all electrical installations, systems, machines, and equipment must have a protection system against Earth leakage. The most commonly used and conventional protection is providing an earthing or grounding connection to every electrical installation, device, machine, etc.
Buy providing the earthing or ground connection, we can reduce the chances of electrical shock only, we cannot eliminate the other effects of earth leakage such as voltage imbalance, power loss, etc. So we need a protective device that can sense the earth leakage and trip the whole circuit until we are manually correct or stop the earth leakage.
ELCB and RCCB are protective devices that can give protection and eliminate the effects of earth leakage. ELCB means Earth Leakage Circuit Breaker which is specially designed for the protection of earth leakage from one source only. There are two types of ELCB available, 1. Voltage Operated 2. Current Operated
RCCB means Residual Current Circuit Breaker, it also can be used for the protection of Earth Leakage. The advantage of RCCB over ELCB is, it can sens the earth leakage from anywhere in an electrical circuit and give protection against electrical shock.
Difference Between Earth Fault and Earth Leakage
There is no big difference between Earth Fault and Earth Leakage, just difference is that when a live conductor directly touches the ground or through a very low resistance and causes to flow a very high current then it is called Earth Fault. On the other hand, when a very low current flows from live to the ground due to poor insulation or capacitance effect, then it is called Earth Leakage.
Earth Fault Example: In the overhead transmission line, when accidentally live conductor broken and touched the ground.
Another example is when any live conductor accidentally touches the metallic body of the equipment.
Earth Leakage Example: Leakage due to poor insulation in electrical cables.
Leakage due to capacitance effect in a transmission line or electronic circuits.
Earth Leakage Current Cause, Example, Measurement, Protection
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January 01, 2021
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Reviewed by Author
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January 01, 2021
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