What is electrical grounding system?
Electrical grounding system, or earthing system, is the process of connecting all metallic parts of electrical devices to ground through an electrical low resistance path, to provide safety for humans and devices.
Connecting electrical equipment to the grounding provides an alternative path for fault current.
The fact that electric current flow through the lower resistance path makes grounding electrical equipment a safety matter, in case of electrical fault, the current will go through the grounding cable rather than going into a human body touching the faulty equipment.
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Working principle of electrical grounding
Grounding system provides a low resistance path for static charges and electrical current in fault condition to earth.
In case of electrical faults, currents takes the lowest resistance path. By grounding the device, we give electricity an alternative path instead of human body.
As we know that electrons follow through the shortest possible path in the circuit. If any fault come into the electrical wiring, the electrical grounding will provide the shortest path to your electrical system, And a large amount of electrical current will flow into the ground.
For this process we connect copper conductor with a metal rod in the wiring system. Now these are further connected with panels and are placed deep in to the ground.
Whenever a fault occurs in an electrical system, the grounding system provide the shortest possible path to the current.
Earthing resistance should be less than or equal to 5 Ohms to be effective. The value of the earthing resistance depends on some factors like the soil resistivity, humidity, number of earthing rods and cable size.
Why is electrical grounding important?
- Electrical grounding plays an important role in the safety of electrical wiring system.
- Ground have low resistance, Proper electrical grounding provide shortest path to excessive current and hence protect devices or even the whole electrical system from damage.
- lake of good grounding is dangerous and may lead to equipment failure and human injuries.
Grounding system inspection
Over time, ground rods are degraded due to soil moisture, salt and temperature. This means that the grounding resistance becomes larger than 5 Ohms and the system is not effective for its purpose.
For all the above its important to make periodic maintenance and check the system of earthing.
To do so measure grounding resistance and record its value every three years and visual check and inspect grounding cables and connections for any corrosion and damage.
How to measure grounding resistance?
Its easy job to measure the resistance value of a grounding system using a clamp meter like Fluke 1630-2 FC Earth Ground Clamp, it needs no special training to use it.
Megger earthing meter is another way to measure grounding resistance. The device has three cables, one to connect with the earthing rod, and two others are connected to testing rods, 50cm copper rods.
We dig the testing rods to about 40cm depth, connect them with the device and connect the other cable to the earthing rod to measure its resistance. Turn on the device and you done.
What devices need grounding system?
All metallic parts of electrical equipment such as electrical transformers, motors and generators should be grounded through low resistance cable to earthing system.
In case of the insulation of electrical equipment fails for any reason the voltages which may present on the metallic body of the equipment should find some path to be discharged.
If the equipment is not grounded, these dangerous voltages may transferred to anyone who touches the equipment resulting in dangerous electric shock.
Should I ground my house?
To protect your family against electrical shock you should connect an electrical grounding cable to your house and make proper earthing system for it.
Refrigerators, water electrical heaters, and washers in most cases have a metallic body which mean it can cause an electric shock if the insulation of electrical parts degraded.
Connecting these home appliances to a good grounding system can safe your and your family members lives.
How much should a grounding resistance be?
The ideal grounding system should has zero Ohms resistance, but in real life this ideal system is not exist. So the NFPA and IEEE recommend that the grounding resistance value should be 5 Ohms or less.
Electrical grounding system should provide resistance not more than 5 Ohms, this value can be achieved by one or more copper rods in the ground.
Noting that the ground nature affect the value of the resistance of the earthing rods, So in some cases where ground is so dry the you may need to use more than one earthing rod.
In dry ground cases we use resistance improvement methods like salt, water and coal to enhance the soil resistivity.
How long the ground rod should be?
The electrical grounding rod should be at least 8 feet in depth under ground. And in some cases you may need more than one rod to achieve the proper resistance value of electrical grounding i.e 5 Ohms.
A good design to know the soil characteristics before installing the rods will help in choosing the correct number of rods and the depth of them.
How Does Grounding Prevent An Electric Shock?
Grounding is a method of protecting yourself against electric shock. It accomplishes this by providing a path for a fault current to flow to the ground through a protective conductor.
It also causes the safety device (GFCI) to cut power to the faulty circuit.
A grounding wire redirects the energy accumulated during the malfunction outside your residence and into the earth.
The grounding wire is often attached to a metal internal component or exterior casing within the appliance. Instead of accumulating energy, it flows back to the ground when the circuit fails and shuts off the circuit, and prevents you from an electric shock.
Using this grounding wire, electricity can be discharged safely without causing damage to your appliances or electronics or putting you at risk of electrical shock.
Most electrical outlets, lights, appliances, and electronic products will have a grounding wire as part of their design you should connect this wire the right way to make the device safe.
A grounding wire is often the third prong on the bottom of a circular power plug and is shaped like a triangle.
Can Any Wire Be Used As a Ground Wire?
Yes, any wire can be used as the ground wire. Still, it is best to use oxygen-free, multi-strand Copper grounding wires that are commonly utilized in electrical systems for grounding purposes due to their durability and electrical conductivity.
Considering that electricity is such a powerful source, it is very important to use durable wires. The choice of copper wires varies depending on the specific application. We will explain three of these different copper wires in detail here.
- Bare Copper Conductor: One of the most common types of copper wire used for grounding is bare copper. This copper wire has no protective coating, so it is completely uncovered, hence the name. This type of copper is the most common in residential homes worldwide and is probably the most conductive, without the need for insulation.
- Green 6 THHN: The Green 6 THHN wire is another type of copper wire specifically used for outdoor grounding. It is represented by the fact that it is an outdoor grounding wire due to its green color.
- Gauged Copper: There are different sizes of gauged copper grounding wires.1/0, 2, 4, 8, 10, 12, 14, and 16 gauges are available for you to choose from. The smaller the wire is, the higher the gauge number. Generally, the bigger the copper ground wire in your ground circuit, the more current it can carry.
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Can You Ground with Aluminum Wire?
Aluminum wire can be used for grounding, but copper is preferable since aluminum oxidizes faster and becomes brittle. It is possible that the earthing of an aluminum conductor will not last for very long.
Aluminum has lower electrical conductivity compared to some other metals, which is kind of surprising given how bad the ground is.
While aluminum can be used, it is not the best material for specifically grounding purposes. Despite its poor ground properties, it has a lower electrical conductivity.
Which Is The Better Grounding Rod, Aluminum Or Copper ? As a conductor and earth electrode material, copper is the best choice – solid copper is recommended for high fault current installations, whereas copper-bonded rods are installed for smaller sections.
Can I Touch Earth Wire?
Yes, you can touch the earth wire because, earth wires do not carry any electric current and have exposed cables and connectors. Its safe as long as there aren’t any electrical surges or faults.
An earth wire takes excessive electric current from electrical circuits when a surge or electrical problem is identified. The earthing wire conducts electricity to the earth via a grounding rod or pipe, where it may be safely neutralized.
Wires used for grounding are exposed, especially those running through grounding rods on the outside of your home.
It is safe to touch the grounding wires
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