What Is An Earth Wire And Its Importance To Electrical Systems?

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Earth Wire


Earth wire is crucial parts of electrical circuits. They prevent exposure to electrical shocks. Earth wires connect appliances to the ground. This happens by absorbing extra electrons and channeling them to the ground. As a result, earth cables shield against electric shock from current leakages. 

Electric appliances consist of metallic materials, which conduct any leaks of electric current. Without incorporating earth wires, electric shock can damage the central nervous system. Thus, earthing cable ensures that metallic appliances are safe to use.

1.What is earth wire? 

Earth wire is a protective conductor that helps avoid fire and shock. An earth wire’s function is to provide secure travel for extra electrical charges. The earth’s solid bulk possesses a negative electrical charge. This attracts positive electrical charges.

An earth wire’s role is to regulate and direct charges into the ground. This happens without the risk of electric shock.

Usually, earth cable provides low resistance. This creates a channel during fault situations that safeguard the circuit.

Before selecting the suitable earth grounding wire, discover the best earth cable prices. Also, search a wide selection of wholesale electrical wires from various manufacturers.


The other feature to look at in earth cable is braiding. Usually, braided earth cable plays two significant roles. That is an electrostatic screen or providing the cable with more mechanical strength. For protection against lightning, bare cable earthing is necessary.

Also Read: Get More Out Of Your Earth Cable System

Cable screen earthing is the most effective method of shielding. It protects the earth cable at both ends of the cable. It was once common practice ground the shield’s source end to drop ground loops. The best practice is to ground at both ends. Yet, ground loops are possible.

How earthing prevent electrical shocks

Figure 1: How earthing prevent electrical shocks

2.What is the size of the earth wire?

The application determines the size of the earth wire. Conductor material, temperature, fault current, and length elements affect conductor size.

The type of installation and fault current also determine the earth cable size. IEEE-80 recommends the following factors when choosing an earth conductor.

a) Be conductible to make minimal contributions to regional voltage differences.

b) Withstand mechanical degradation and fusing. This should occur even in the worst-case scenario of a fault’s size and duration.

c) Have a high degree of mechanical dependability and toughness.

d) Be able to continue operating even when subjected to physical harm or corrosion.

The formula to calculate the cross-section of the earth cable is;



A = Earthing conductor cross section (mm2)

I = RMS current kA

TCAP = Thermal capacity per unit volume, expressed in J/(cm3 °C)

tc =  time of current flow in s

αr – thermal coefficient of resistivity in 1/°C

ρr – resistivity of the ground conductor in mΩ-cm

Ko – 1/α o or (1/α r) – Tr in °C

Tm – the greatest allowable temperature in °C

Ta – ambient temperature in °C

The least earth wire for a modest household electrical circuit is 16 swg, or 1.5 sq mm diameter. This earth cable size helps protect electrical equipment from electrical shock. The earth wire gauge also protects hidden wiring within the PVC pipes.

A 35 sq. mm single core cable is more suitable for handling greater electrical circuit capacities. E.g., ideal for operating an induction motor with 100 HP or 75 k.

6mm twin and earth cable is flat for simpler installation into plaster. This cable gives internal power to equipment like electric showers and cookers. Using earth cable 10mm is appropriate for underground installation and building attachment. The cable is also part of telecommunications networks.

2.5mm cables are valuable for domestic use, such as power sockets and circuits. This twin and earth cable consists of two cores and an earth core.

3.Is the grounding wire necessary?

The grounding wire is crucial. If the usual channels are impassable, this earth wire uses a cable to act as a path for electrical current to flow. This can be the case if there is too much electricity or if the other pathways are not functional.

In simple terms, the grounding cable is suitable when experiencing a breakdown. It also protects equipment from excessive charges. This is because the extra electricity passes via earth cable and into the earth.

An excellent example of the application of grounding wire is in the battery earth cable. The earth bonding cable grounds the battery by connecting it to the vehicle’s chassis. They work together to form a closed loop that lets power flow.

4.Why is the earth cable thicker than the live and neutral wire?

Earth cable has a larger cross-section, thus lower resistance. This allows more current to flow through it in the event of a short circuit.

In the event of a failure, the current flow is higher than usual. Thus, a thicker conductor can handle the higher current since it has a low resistance.

The fault current, 50 times the rated current, passes via the earth wire. Thus, a thicker diameter wire is suitable for evacuating fault current.

Additionally, this makes third sockets in homes have greater diameters than ph-neutral sockets. In a 3-pin plug, the Earthing pin is also thicker.

The rule of resistance is the second argument in support of thicker pins. The formula for resistance is as follows;

R = ρ (L/a)

Where: R = Resistance, ρ = Resistivity, L = Length of the Conductor, and a = Area of the conductor

The formula shows that resistance decreases with thickness. It demonstrates that the resistance is inversely proportional to the conductor’s area. In other words, the resistance decreases as the conductor thickness increases.

In this instance, a leakage current occurs whenever a wet body comes into contact. It allows current to pass through as it chooses the least resistance possible.

It is worth noting that a thicker earth cable or pin does not provide total immunity to electric shock. So there is still a probability of receiving an electric shock.

Usually, the cross-sectional area varies with the size of the earth wire. For instance, 1.5mm and 2.5mm earth cables have a cross-sectional area of 1mm and 1.5mm, respectively.

Depending on the thickness, there is various use of different cable earth. For instance, 3 Core and earth Cables are helpful for two-way lighting setups.

These earth cables also apply in other circumstances, like extractor fans. The wires are also suitable for central heating and various forms of lighting.

Thicker part of a 3-pin plug

Figure 2: Thicker part of a 3-pin plug

4.Why is the earth wire yellow and green?

Yellow and green earth cables replace the old earth cable color red, black, and green in 2006. If you may still have these old earthing wires, you should change to the modern yellow and green earth cable.

It is usual to encounter green/yellow soil ground. This defines the earthy ingredients of green and yellow color in earth wire. So, the green and yellow cables are perfect for cable ground and grounding purposes.

Green/yellow wire is most seen in electrical or automotive circuits’ in-home wiring.Thus we can called it house wire.

Also Read:The Safety Of Your House Wire Depends On It

These colors make uses of the earth cable easy. One may grasp the ground wire’s color if familiar with its purpose. Usually, Earth wires come in three main categories. One is green; the other has a yellow stripe running.

Green and yellow strips in an earth cable

Figure 3: Green and yellow strips in an earth cable

5.What happens if I do not connect the earth cable?


If there is no earth wire, there is a risk that the live wire will touch the casing if a failure develops. The device might electrocute the person who uses it after them.

The earth wire offers a low resistance path to the ground since it comprises copper. In the event of a malfunction, the current flowing through the earth cable will take this route. as a result, it will protect against blowing a fuse and making the appliance safe.

But, not all devices and equipment must have the earth cable. So you can use them without worrying about electric shock. For instance, vacuum cleaners lack an earth wire.

Two bad things may occur if there is no earth cable. First, ground zero cables will not have a ground reference. This leads to irregular and inconvenient voltages that could harm equipment.

But more importantly, unwanted fault currents will not have a path back to the source. This is necessary for tripping overcurrent protection devices.

The frame receives a fault current if a gadget has no earth wire. So, the fault current electrifies the whole panel.

If the earth wire is in proper connection to the ground, the safety device will trip. This opens the circuit when the fault current returns to the source. Then it takes the voltage and current from the malfunctioning device and restores it.

Earthing armoured cable is necessary unless it has adequate mechanical protection. Earth cable sheath provides use as a protective conductor. connection of earth cable in-home appliance

Figure 4: connection of earth cable in-home appliance


Earth wires provide effective preventive measures against electrical shock. In this situation, the cables save life and the cost of repairing or purchasing new appliances.

An earthen cable discharges electrons to the ground for safety and functional reasons. Thus, the choice of earth cables influences the installation’s safety and electromagnetic compatibility.


Last Updated on September 14, 2022 by Richard

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Richard Zi

Hey, I am Richard Zi, General Manager of ZW Cable and expert in cable industry for over 15 years. I would like to share my experience in cable field. ZW Cable is leading Chinese cable manufacturer. We can choose right size cable and solve all your cable problem. If you have any question, please feel free to contact me. I will try my best to give your cable solutions.

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