What should be the value of earthing resistance?

What should be the value of earthing resistance?

5.0 ohms
Ideally a ground should be of zero ohms resistance. There is not one standard ground resistance threshold that is recognized by all agencies. However, the NFPA and IEEE have recommended a ground resistance value of 5.0 ohms or less.

How is earthing value calculated?

Example: Calculate Total Earthing Rod Resistance of 200 Number arranges in Parallel having 4 Meter Space of each and if it connects in Hollow Square arrangement. The Earthing Rod is 4 Meter Long and having 12.2mm Diameter, Soil Resistivity 500 Ω. R=500/ (2×3.14×4) x (Loge (8×4/0.0125)-1) =136.23 Ω.

How do you test earth resistance?

Earth resistivity is usually measured using the Wenner method, which involves the use of four temporary earth spikes. The spikes do not need to be moved as part of the testing procedure however – their location and spacing is determined by the depth at which it is required to determine the earth resistivity.

What is the acceptable earth resistance value UK?

In most parts of the UK an earth electrode resistance in the range 1 Ohm to 5 Ohms is considered to be acceptable.

What is the resistance of earthing electrode?

The earth resistance mainly implies the resistance between the electrode and the point of zero potential. Numerically, it is equal to the ratio of the potential of the earth electrode to the current dissipated by it. The resistance between the earthing plate and the ground is measured by the potential fall method.

What is the acceptable earth resistance value in India?

The acceptable Earth Resistance at earth MEEB busbar shall not be more than 1 ohm. For achieving this value more than one earth pits can be installed if necessary depending upon the soil resistivity.

What is a good earth electrode reading?

The earth electrode, where used, is the means of making contact with the general mass of earth. If a 30 mA RCD is used, this allows a maximum electrode resistance of 1,666 Ohms, although it is recommended that earth electrode resistance should never be greater than 200 Ohms.

What is the earthing resistance?

Earth resistance is the resistance of the soil that is occurred during the passage of electric current. It can also be defined as the resistance between infinite earth and earth electrode.

What is the acceptable earth resistance value IEC?

10 Ω
The recommended value of the overall earth resistance of 10 Ω is fairly conservative in the case of structures in which direct equipotential bonding is applied. The resistance value should be as low as possible in every case but especially in the case of structures endangered by explosive material.

How do you test the resistance of an earth rod?

An alternating current (I) is passed through the outer electrode C and the voltage is measured, by means of an inner electrode P, at some intermediary point between them. The Earth Resistance is simply calculated using Ohm’s Law: Rg = V/I.

What factor does earth resistance depend on?

It is the resistance of the soil to the passage of electric current. It varies from soil to soil. It depends on the physical composition of the soil, moisture, dissolved salts, grain size and distribution, seasonal variation, current magnitude etc.

How do you test a 25 ohm ground rod?

Check the resistance reading on the meter. Your clamp-on ground tester will have a screen that will show you a numeric reading. The lower the number on the meter, the better your grounding rod is working. In general, a reading under 25 ohms means that your ground rod has a good connection to the earth.

What is the value of an earthing system?

The value of earthing resistance depends upon the the construction design , soil resistivity and also the climatic condition. Moisture content in soil plays a big role in the soil resistivity. value of individual earthing pit resistance is not so important. different codes specifies the required value of earthing system .

How is the resistivity of an earthing rod calculated?

The earthing rod is 4 meter long and having 12.2mm diameter, soil resistivity 500 Ω meter. R=500/ (2×3.14×4) x (Loge (8×4/0.0125)-1) =156.19 Ω. The earth resistance of single rod or pipe electrode is calculated as per IS 3040: R=100xρ/2×3.14xL (loge (4xL/d))

When to use more than one earthing electrode?

In cases where a single electrode is not sufficient to provide the desired earth resistance, more than one electrode shall be used. The separation of the electrodes shall be about 4 m. The combined resistance of parallel electrodes is a complex function of several factors, such as the number and configuration of electrode the array.

Why is earth resistance important in lightning arrester?

As you will see, earth resistivity has an important bearing on electrode resistance, as does the depth, size and shape of the electrode. The principles and methods of earth resistance testing covered in this section apply to lightning arrester installations as well as to other systems that require low resistance ground connections.