What is electrical grounding system?
Electrical grounding system, or earthing system, is the process of connecting all electrical and metallic devices to grounding system through electrical low resistance path to provide safety for humans and devices.
Working principle of electrical grounding
Grounding system provides low resistance path for static charges and for electrical faults to earth. In case of electrical faults, currents takes the lowest resistance path. By earthing 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 the electrical experts 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. The current follows the shortest path and as a result a device or anything is prevented from large amount current flow.
Types of electrical grounding
Electrical grounding is divided in two different type. The first one, is neutral grounding, the second one is Equipment grounding. Let’s discuss each one of them below.
Neutral grounding, the neutral part or wire of a system is connected directly to the earth. Some times it is also referred with system grounding.
If a system has star winding the best possible way to ground the system is neutral grounding. The example is generator; the neutral of the system is directly connected to earth by the help of the GI wire.
The neutral grounding is also called the system grounding. Such type of grounding is mostly provided to the system which has star winding. For example, the neutral grounding is provided in the generator, transformer, motor, etc.
This type of grounding is used for electrical equipment. In this type of grounding the neutral part is connected with ground by using of metallic wire. In case of any fault, the short circuit current flows into the ground via the metallic wire.
This earthing type is important for all metallic parts that has electrical power source, such as electrical motors, generators, panels and switch-gears, This grounding is to protect both human and equipment as well.
When a person touches the metallic part then the electric shock is prevented by making a low resistance path for the current, this path is through grounding cable.
Why is electrical grounding important?
- Electrical grounding plays an important role in the safety of electrical wiring system.
- Grounding distributes the power due to which it helps to maintain the voltage level in stable condition.
- 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.
Grounding system inspection
Over time, ground rods are degraded due to soil moisture, salt and temperature.. This means that the grounding resistance become 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, 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.
What devices need grounding 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.
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 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
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
How Does Grounding Prevent An Electric Shock?
Grounding is a method of protecting yourself against electric shock. It accomplishes this by providing a conduit for a fault current to flow to the ground through a protective conductor. It also causes the safety device (either a circuit breaker or a fuse) 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.
A grounding wire is often the third prong on the bottom of a circular power plug and is shaped like a triangle. To ground your electrical wiring, there has to be some way to connect it to the soil outside of your home.
In most cases, an 8-foot-long copper rod is driven into the soil outside your home for grounding purposes. It’s positioned far enough away from your house so it won’t collide with the gravel, concrete, or other building materials used for your foundation, drainage, or piping system.
Can Any Wire Be Used As 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 .A copper grounding wire such as this is insulated and can be used outdoors without any concerns about moisture getting to the copper wire itself. The wire is not only to be considered a ground wire outdoors, but it can also serve as a conductor.
- 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.
For more information about electrical conductors, you can check out my detailed article here.
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.
Earthing electrodes are specifically designed and installed to improve a system’s grounding. To minimize resistance, the earth electrodes must penetrate the moisture level below the ground level. Earth rods are frequently used for their corrosion resistance.
The cost factor is also an important consideration in selecting. All too frequently, the cost of a product is seen as the original purchase price, while the ground rod’s usable life decides the true cost.
Galvanized steel rods are among the most affordable electrodes available. However, they are not the most cost-effective due to their very limited-service life.
The service life of solid copper and stainless-steel rods is quite lengthy. They are, nevertheless, significantly more costly than galvanized steel rods.
Furthermore, solid copper rods are not suitable for deep diving into the hard ground due to the possibility of bending.
With copper bonded earth rods, there is a compromise between these two alternatives. It features a copper electrolytic covering placed over a nickel layer. This procedure aids in the formation of a long-lasting molecular link between the copper layer and the steel core.
Copper bonded ground rods are preferred over copper wrapped electrodes because the copper covering will not slip or rip when driven, nor will it split if the rod is twisted.
Compared to other earth rods, copper bonded earth rods have high corrosion resistance, provide a relatively low resistance path to the ground, and are good for deep driving.
How Far Should A Ground Rod Stick Out Of The Ground?
It is important to drive the rod as deep as possible. The minimum recommended depth to drive the rod into the ground is 8 feet.
A minimum of 2.44 meters (8 feet) of the electrode length must be in contact with the soil. The electrode shall be driven at a depth of not less than 2.44 m (8 ft), but if an oblique angle is encountered, it shall be driven at a 45-degree angle not exceeding 45 degrees from the vertical or be buried in a trench at least 750 mm (2 1/ 2 ft) deep.
An electrode’s upper end shall be flush with or below ground level unless the above ground end and the grounding electrode conductor attachment are protected against physical damage.
Why Are Some Appliances Not Need Grounding?
Some equipment and power tools, such as vacuum cleaners and power drills, not need grounding. The reason for this is that they have plastic casings or are constructed in such a way that the live wire does not touch the casing.
As a result, even if the wires within fall lose, the shell cannot provide an electric shock to the user. This is called, double insulated devices.
What are double insulation devices?
Electric appliances have two layers of insulating materials, which separate the electrical parts of the appliance from any components on the outside that can be touched, called double isolation devices.
To protect people from electric shock, double insulation is introduced. For example, in most countries today, every power tool operated on mains voltage must be certified as meeting double insulation requirements. Thermoplastic is used to insulate the motor’s armature core and stator core before copper is wound onto them.
The motor shaft is not welded directly to the rotor core but rather insulated using a resin filler. In the event of a failed insulation, this stops high voltage from the armature windings from leaking into the motor shaft.
In order to prevent electric shocks to the operator, the entire outer shell of the power tool must be made of plastic.
Most modern power tools don’t even require Protective Earth wires with all these arrangements. Hence, they are referred to as Double Insulation Compliant.
How Do You Know If An Appliance Is Double Insulates?
The double insulation protection of appliances indicated with the double square sign, indicates that the equipment is double insulated. You can find this sign on the device body. An appliance classified as Class II protection does not require a connection to electrical earth.
There is usually a plastic cover on a Class II appliance. In order to accurately identify it, you must look for the Class II appliance symbol. Hairdryers, DVD players, televisions, computers, and photocopiers are examples of Class II appliances.
Equipment with double insulation would normally be inspected as part of your ongoing PAT Testing regime. Still, it would likely not need to be inspected as a class I appliance subject to regular portable appliance testing.
Which Home Appliances is Double Insulated?
Hairdryers, DVD players, televisions, laptops, photocopiers, blenders, coffee makers, air blowers, drills, refrigerators, kettles, vacuum cleaners, and phone chargers are common examples of double-insulated household equipment.
This sort of appliance and tool is referred to as “double insulated.” They contain two layers of insulating materials between the appliance’s electrical components and any elements on the outside that you contact.
Why Are Some Appliances Double Insulated Instead Of Earthed?
Because double insulation prevents any possibility of the outer casing becoming live, it eliminates the need for an earth connection, thus protecting the user from an electric shock.
The double or reinforced insulation method involves adding supplementary insulation over the basic insulation or placing a single layer of reinforced insulation directly over the live parts to protect against electric shock.
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.
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.
The third and round plug on modern electrical outlets is the grounding wire connection for electrical equipment that may need to redirect electricity from causing electrocution.
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 as long as there aren’t any electrical surges that could cause electricity to flow through the wires.
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