- Ground and Earth are two important terms for Instrumentation and Electrical Engineers in making electrical wiring for a particular process control system.
- Though many times we came across the words ground fault as well as earth fault which are similar to each other.
- Now let us look at what is the actual difference between ground fault and earth fault.
- A ground fault is a type of fault that occurs due to contact between a ground point or neutral point and a live conductor.
- In-ground fault and the current directly starts flowing to the ground due to that contact.
- A ground fault, on the other hand, occurs when there is a fault or malfunction in an electrical system that causes electricity to flow through an unintended path, such as a conductor that is not intended to carry an electrical current. This can happen if a conductor becomes damaged or fails and electricity begins to flow through it, or if an electrical device is improperly installed and electricity flows through it.
- During a ground fault, the magnitude of the flowing current is very high because of the low resistance path for the current to flow through the live conductor.
- A huge amount of current flow in the ground causes a loss of energy.
- Here, the ground fault may be in a single (L-G) phase to ground, or more than one phase to ground (LLG) or LLLG.
- Ground Faults are more dangerous compared to Earth Faults due to the large current flow.
- If this fault is not cleared or solved within a specified time, then there may be serious damage to various equipment of a power system.
Reasons/Causes for Ground Fault:
- Overheating of the cable due to high current flow or material defects.
- Insulation damage or loss of dielectric property due to aging.
- Physical damage in an underground cable.
- Water enters the cable drench or the insulator.
- The conductor may cut and fall into the ground point due to an overload of the cable.
- Descending of wide trees into the conductor due to some Natural disturbance such as turbulence or cyclone so that when living things touches live wire and ground point.
- During hurricanes and thunderstorms, the overhead line conductors might come in contact with branches of the neighboring tree.
- The ground fault also occurs due to short circuits in any component and the breaking of the overhead conductor.
- Physical contact of any ground wire with a live conductor or live circuit causes a ground fault
- The loose connection causes an increase in contact resistance & thus there would be higher heat generation at points of contact.
- The insulation life may drop if operated above the specified temperature range and may damage the insulation
- Water ingress or the presence of moisture in any electrical panel, marshaling panel, control panel, or junction box.
- During the maintenance period on the live conductors if the live conductor touches the ground by mistake then there is a chance of occurrence of the ground fault.
Various types of Ground faults:
Ground faults may occur in three ways.
1. Single–Line-to Ground Fault(L-G fault):
In a single line-to-ground fault type,
- Only one live phase Blue contacts the ground.
- Here, the flow of fault current exists between the live phase and the ground.
- But, the remaining two healthy phases supply the required fault current.
2. Double-line-to Ground Fault(L-L-G fault):
In a Double line to ground fault type,
- Two live phases Blue and Yellow contacts the ground.
- Here, the flow of fault current exists between these two live phases and the ground.
- But, the remaining third healthy phase Red supplies the required fault current.
3. Triple-Line-to-ground fault (L-L-L-G Fault):
In a Triple line to ground fault type,
Here, the flow of fault current exists between all three live conductors touching the ground.
- Earth fault is known as an Open Circuit ground fault.
- An earth fault occurs when there is a fault or malfunction in an electrical system that causes electricity to flow through the earth, rather than returning to the electrical source through the intended path. This can happen if a conductor, such as a wire, becomes damaged or fails and electricity begins to flow through the ground.
- In other words, If any live conductor power-carrying cable gets unlinked from its location and descends on the ground surface and gets into direct contact with the earth, this fault current flows from the phase conductor to the ground because the surface of the earth is conductive type or very good conductor of electricity.
- A huge amount of current starts flowing to earth due to conducting nature of earth because the live conductor and Earth have direct contact between them.
- When any humans, other living beings, or any equipment come in contact with this loop may get affected due to the current flowing in it.
- The main cause of earth faults in an overhead transmission and distribution line is the failure or puncture of the insulator. Since insulators are used in overhead transmission lines to provide insulation between the live conductor and metallic towers that are already connected with the earth’s surface.
- A device called megger is used to check and identify the earth leakage fault in cables.
- Earth fault protection devices are electrical types of equipment that protects earth fault and are used during electrical installation
Earth fault protection devices are classified as ,
1. Earth Fault Relay (EFR):
- Is an earth fault monitoring device
- Its working is based on the concept of Kirchhoff’s laws.
- EFR functions at higher voltage and high current range.
- It is a protection device that detects the fault between phase and earth.
- This device provides electrical protection to equipment from earth faults.
2. Earth Leakage Circuit Breaker (ELCB):
- It is acclaimed as Residual Current Circuit Breaker (RCCB).
- It is a special type of circuit breaker that is used to assure good protection against earth leakage current.
- It is a protection and safety device with high earth impedance.
- It is a voltage-detecting device that works on the principle of stray voltage.
- It gives good protection to the human body and prevents electrical shock
- But, the main thing is that this device doesn’t provide any kind of protection against overloading and short-circuit faults.
Reasons/Causes for Earth Fault:
- If any cable cuts and descends the earth from a lightning or supply pole during the rainy season due to high-velocity wind.
- Another possibility of an earth fault is during the maintenance activity of a live conductor if it comes in contact with the earth by mistake. And the floating ground is used in plants
Both earth faults and ground faults can be dangerous, as they can cause electrical shock or fires. It is important to properly maintain and repair electrical systems to prevent these types of faults from occurring.
How to avoid Ground fault and Earth Fault?
A ground fault occurs when electrical current flows through an unintended path, such as through water or a person, rather than through its intended path through a conductor.
To avoid ground faults, it is important to follow proper electrical safety practices and maintain good electrical system maintenance.
Some specific steps that can help reduce the risk of ground faults include:
Ground & Earth Fault Circuit Interrupters (GFCIs & EFCIs):
These devices are designed to detect ground and earth faults and automatically interrupt the flow of electricity to prevent electrical shock. GFCIs and EFCIs should be installed in areas where there is a risk of ground faults and Earth faults.
Proper Wiring Techniques:
Make sure that all electrical wiring is properly installed and maintained. This includes using the correct wire size for the intended load and ensuring that all connections are secure.
Avoid overloading circuits:
Overloading a circuit can increase the risk of ground and earth faults. Make sure that the total electrical load on a circuit does not exceed the circuit’s rating.
Use proper outlets and plugs:
Make sure that all outlets and plugs are in good condition and compatible with the electrical devices that are being used.
Use proper extension cords:
If you need to use an extension cord, make sure it is rated for the intended use and that it is in good condition. Do not use damaged or frayed cords.
By following these safety guidelines, you can help reduce the risk of ground and earth faults and ensure the safety of your workplace.
Ground fault and Earth Fault monitoring methods:
There are several methods that can be used to monitor for ground faults and earth faults and detect when they occur. Some common methods include:
Ground fault and Earth fault circuit interrupters (GFCIs):
These devices are made to recognise ground and earth faults and automatically stop the flow of energy. Circuit breakers, outlets, and portable electrical equipment can all have GFCIs and EFCIs installed.
Ground and Earth fault relays:
These devices are used to detect ground and earth faults in electrical systems and trigger an alarm or shutdown in response. Ground and earth fault relays can be used to protect individual circuits or an entire electrical system.
Ground and Earth fault detectors:
These devices can be used to continuously monitor an electrical system for ground and earth faults. They may be portable or permanently installed and can provide an immediate alert when a ground or earth fault is detected.
Electrical testing equipment:
A variety of electrical testing equipment, such as resistance meters and ground testers, can be used to check for ground and earth faults in electrical systems. These tools can help locate the source of a ground and earth fault and identify any damaged or faulty components.
By using one or more of these methods, it is possible to continuously monitor an electrical system for ground and earth faults and take appropriate action to prevent accidents or damage.
How to test for a ground and earth fault?
There are several methods that can be used to test for ground or earth faults in an electrical system. Some common methods include:
A resistance meter, also known as an ohmmeter, can be used to measure the resistance between different parts of an electrical system. If a ground or earth fault is present, the resistance readings may be abnormal, indicating a problem.
A ground tester is a specialized device that is used to test for any faults. It can be used to test outlets, extension cords, and other electrical components.
A continuity tester is a device that is used to test the continuity of electrical circuits. It can be used to test for any faults by measuring the resistance between different parts of an electrical system.
A multimeter is a versatile tool that can be used to measure a variety of electrical quantities, including voltage, current, and resistance. It can be used to test for any faults by measuring the resistance between different parts of an electrical system.
To test for a ground or earth fault, you will need to follow the manufacturer’s instructions for your specific testing device. In general, you will need to connect the device to the electrical system and measure the resistance between different points. If a ground or earth fault is present, the resistance readings may be abnormal, indicating a problem.
Protecting a System from Ground Fault and Earth Fault
Some basic protection steps need to be followed to protect the system from ground fault and earth fault
- Generally, protection relays are used to trip the system under faulty conditions such as detection of over-current or overvoltage.
- MCB and Fuse provide protection to some extent during fault conditions.
- Using Earth Leakage Circuit Breaker or Residual Case Circuit Breaker in domestic applications.