Earth Resistance Calculation using Ground Mat

[src982]

Hi,

I am recent graduate as Electrical Engineering and working in the grounding design with various configuration. I just have the querry regarding how to estimate the Grounding Resistance using Ground Mat considering the effect of soil resistivity, Mat sizing, and conductors.

It would be great assist to me.

Thank you.

 

[Hameedulla-Ekhlas]

Hi,

I am recent graduate as Electrical Engineering and working in the grounding design with various configuration. I just have the querry regarding how to estimate the Grounding Resistance using Ground Mat considering the effect of soil resistivity, Mat sizing, and conductors.

It would be great assist to me.

Thank you.

Welcome to forum,

The following steps should be followed for the design of an earthing grid:

(a) Data needed for design:

1- ground area
2- soil resistivity at the site
3- fault clearing time
4- maximum grid current
5- resistivity of soil at surface

(b) Design of eathing system

1- Selection of electrode material
2- Determination of conductor size
3- Preliminary design
4- Determination of conductor lenth required for control of voltage gradient
5- Calculation of resistance and ground potential rise
6- Checking of step ptential and revision of design, if necessary.


These are all the topics you have cover. So, I can not go in detail of each for you and it takes alot of time. Please find out the detail in power system books.

 

[src982]

Hi

Hi

Thank you for the information. What I am actually looking out here is approximate formula to estimate the Grounding resistance if we use the ground Mat which might be only function of soil resistivity, its size and depth below the soil surface.

If anyone come up with good suggestion and idea , it would be greatful.

Thank you.

 

[jghrist]

IEEE Green Book?
IEEE Std 142?-2007? Recommended Practice for Grounding of Industrial and Commercial Power Systems

This has several formulas for calculating resistance of different grounding electrodes.

See http://standards.ieee.org/colorbooks/sampler/greenbook.html

 

[Hameedulla-Ekhlas]

Thank you for the information. What I am actually looking out here is approximate formula to estimate the Grounding resistance if we use the ground Mat which might be only function of soil resistivity, its size and depth below the soil surface.

If anyone come up with good suggestion and idea , it would be greatful.

Thank you.

Find out this

IEEE Std 80-2000 - IEEE guide for safety in AC substation grounding

 

[src982]

Resistance calculation of grounding mat.

Resistance calculation of grounding mat.

Thank you for the suggestion regarding Green Book of Grounding and IEEE Std-80. I have gone through the books and did not find the exact formula for rectangular ground mat . It has for buried horizontal round plate and buried vertical round plate.

Any additional information would be appreciated.

Thank you.

 

[rcwilson]

There is no simple equation. Go back to IEEE 80 and read it thoroughly.

If you just want an estimate of the grid resisstance, look at the charts in Appendix C. Read through the calculation examples in Appendix B.

You can get a lower limit estimate of the resistance using equations 50 & 51 (Laurent's and Nieman's) in IEEE 80 or Sverak's.

But note that these calculations tell you nothing about whether the grid is safe for step and touch voltages during a fault.