Have you ever wondered why we do earthing or ground systems in our homes, do you know they offer protection to us and our buildings? Well, I will tell you why good earthing is a must-have in our homes.
An electrical earthing or ground system is an act of connecting the metallic parts of an electrical system to the ground.
It is the connection of the neutral points of an electrical system such as the metallic casing, stay wires, and earth terminals of socket cables to the earth electrode usually buried in the ground.
Grounding helps prevent electrocution whenever there is an electrical discharge. It also protects our building from lightning.
Importance of a good earthing system
Grounding plays an important role, they include:
- Offers lightning protection
- Protection against electrical overload
- Helps direct currents
- Stabilize voltage level
- Prevents electric shock.
Components of an earthing system
A good earthing system comprises:
- Earth cable
- Earthing Lead
- Earth plate, or electrode
This is the wire that connects all the metallic parts of an electrical system such as the distribution boxes, plug sockets, fuse, and metallic shells. Metallic parts of machines such as transformers, generators, motors.
The cable must be of low resistance as per IEEE law, which states that the resistance between the consumer earth terminal and the earth continuity conductor must be less than one (1) ohms.
Earthing lead or joint
This is the copper wire or conductor that connects the earth cable and the electrode. The point at which the earth cable joins with the earthing lead is the connecting point.
The earthing lead must be straight, lower in size, and must have a few joints.
Although we often use copper wires as earthing lead, copper strips are preferable for high installations as they carry a higher amount of faulty currents because of their wider area.
We may also use hard drawn bare copper wire as an earthing joint. In such a case, we connect all the earth conductors to one connecting point, before using earthing joint to connect it to the electrode (earth plate).
To increase the protection of electrical installations, we use two copper wires as an earthing joint to connect the device’s metal body to the earth plate. When there are two earth plates, the earthing lead, or joint should be four, to improve their carrying capacity.
Earth plate or electrode.
This is a metallic plate usually buried inside the ground. It is the last part of an electrical grounding system. A good electrode must have a low resistance to carry the faulty current to the ground.
Types of electrical earthing
Several types of grounding exist, they include
- Strip or wire earthing
In plate earthing, a copper plate, or galvanized iron (GI) is buried vertically in the ground at a depth of 3 meters and above from the ground level.
It is also important to maintain the earth’s moisture around the plate for a better electrical grounding.
This is the best and the most common type of grounding system. It requires an open pipe made with galvanized iron. The pipe is buried vertically in the ground. The size of the pipe depends on the amount of current, and the moisture content of the soil.
Although the diameter of the pipe is usually 40mm, and 2.75m for normal soil, the moisture of the soil will show the length of the pipe to be buried.
Strip or wire earthing
This is the type of grounding system used in transmission. It requires a strip electrode of cross-section not less than 25mmX1.6mm. The electrode is buried horizontally in a pit of no less than 0.5m. If you use copper for the grounding, the dimension should be 25mm x 4mm, but if it is galvanized iron, it should be 3mm square.
If you are using a round conductor made with galvanized iron, be sure that the cross section is not less than 6mm square. Also, the length of the conductor buried in the ground should not be less than 15m.
Method of electrical grounding
Below are the steps to a good electrical earthing
- Dig a pit of about 1.5 by 1.5m in the ground. Note that the depth and width of the pit will depend on the nature of the ground.
- Bury a copper plate of about 600 x 600 x300m vertically in the pit.
- Tighten the earth’s lead with bolts from the earth plate.
- Use two earth leads to tightening each plate.
- Rub grease on the earth’s joints to prevent corrosion.
- Connect all the wires to the metallic pipe from the earth electrode. Also, be sure that the pipe is at least one foot above the Earth’s surface.
- Use about a 1-foot layer of powdered charcoal, mixed with lime around the earth plate to maintain the soil mixture.
- Make sure that the earth cable which is connected to the metallic parts of all installations is tightly connected to the earth lead.
- Using your earth tester, test the earthing system to make sure it is working fine before filling the pit. Note, the earthing resistance should not be more than 1Ω. If it is above 1ohm, increase the size (not the length) of the earth cable and lead. Keep the external ends of the pipe open to water it often, to maintain the moisture condition around the earth electrode, which is necessary for a better earthing system.