Causes. Earth Potential Rise (EPR) is
caused by electrical faults that occur at electrical substations, power plants
, or high-voltage transmission lines. Short-circuit current flows through the plant structure and equipment and into the grounding electrode.
How can we increase earth resistance?
- Increase the Rod Thickness. …
- Increase the Rod’s Length. …
- Use of Multiple Rods. …
- Treat the Soil to Decrease its Resistivity.
How is earthing resistance reduced?
Another way to lower earth resistivity is
to treat the soil with a salt
, such as copper sulfate, magnesium sulfate, or sodium chloride. Combined with moisture, the salts leach into the soil to reduce earth resistivity. However, this inexpensive process can also cause problems.
What is the resistance of earthing?
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.
What are the factors affecting the earth resistance?
- Soil type. Rocky soil or gravel has especially high resistivity.
- Moisture content level. Dry ground, like sand in a desert, is highly resistive.
- Temperature. …
- Mineral content. …
- Contaminants.
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 will happen to the value of earth resistance if length of the earth pipe is increased?
Since resistance is proportional to length, hence resistance will increase
when length increase
. From the above points we can conclude that, when length of earth pipe is increased the earth resistance will also increase.
How can we solve earthing problem?
- Shut off the main electrical power.
- Find the grounding rod driven into the ground. …
- Check the ground connection clamp. …
- Check the ground wire running to the copper or galvanized water service inside the house.
Which is not method of improving earth resistance?
Chemical treatment
is not a permanent way to improve your earth electrode resistance. The chemicals are gradually washed away by rainfall and natural drainage through the soil.
Which type of earthing is used in homes?
In Plate earthing,
a copper plate (of dimension 600mm x 600mm x 3.15 mm) or a GI plate (of 600mm x 600mm x 6.3 mm)
is used as an earth electrode. The GI plates are frequently used nowadays. The plate is kept with its face vertical, and embedded 3 meters into the ground.
What is the minimum depth of electrode to reduce earthing resistance?
(2) Depth of Ground Rod:
As per NEC code minimum ground electrode length of
2.5 meters (8.0 feet)
to be in contact with the soil. Doubling depth of Rod theoretically reduces resistance 40%. Earthing Spike (electrodes) deeper is a very effective way to lower Earthing resistance.
Why system earthing is different in utilization than equipment earthing?
In grounding
the equipment is not physically connected to the ground
, and the current is not zero on the ground, whereas in earthing the system is physically connected to the ground and it is at zero potential.
Which earthing is used in rocky soil?
Ring Earthing (Type – B)
In rocky or stony ground, surface earth electrodes such as ring or radial earth electrodes are frequently used and it is the only way to create an earth-termination system.
What are the factors which affect the resistance of Earth and how Earth resistance can be reduced?
Pure water is poor conductor of electricity. Resistivity of soil depends on resistivity of water which in turn depends on
the amount and nature of salts dissolved in it
. Small quantity of salts in water reduces soil resistivity by 80%. Common salt is most effective in improving conductivity of soil.
What is the difference between earth resistance and earth electrode resistance?
Definition: The resistance offered by the earth electrode to the flow of current into the ground is known as the earth resistance or resistance to earth. The earth resistance mainly implies the resistance between the electrode and the point of
zero potential
.
What is the value of wet earth resistance?
From Table 3 and Table 7, it is observed that the minimum values of the measured and the calculated (simulation) ground resistances, with the application of grid with rods for the wet soil, are found to be
7.08 and 7.24 Ω
, respectively.
