Program for grounding analysis
Program for grounding analysis
(OP)
hi friends,
I'm looking for a CHEAP but effective software for the grounding grid analysis. Could you suggest anything?
On the other hand, I could write by myself the prg, if somebody could suggest the basic algorythm.
Thank you
Alex68
I'm looking for a CHEAP but effective software for the grounding grid analysis. Could you suggest anything?
On the other hand, I could write by myself the prg, if somebody could suggest the basic algorythm.
Thank you
Alex68






RE: Program for grounding analysis
Two others that I am aware of are by SKM at www.skm.com and CYME at www.cyme.com.
RE: Program for grounding analysis
I know very well these programs.
Usually I use CYMGRD, its biggest problem is the high cost.
All of these programs don't import the grid from Autocad, exept for CYMGRD because I asked to add this possibility.
I think that the best prg is produced by Sestech, that is by Mr. Dawalibi, "the earthing man"!
I'm looking for something cheaper if possible. I would like to start an indipendent activity but the initial budget is low. I'm ready to write by myself the prg, if sombody could suggest the basic algorythm
RE: Program for grounding analysis
You could do a simplified analysis on a spreadsheet or math program like MathCad, based on the calculations given in IEEE std 80, Guide For Safety In AC Substation Grounding. To adequately handle complex grid layouts or multi-layer soils, however, you would need to write a very complex program. A couple places to start would be:
F. Dawalibi, D. Mukhedkar, "Optimum design of substation grounding in two layer earth structure", Part I, II, & III, IEEE Transactions, Vol. PAS -94, No. 2, Mar/Apr 1975, pp. 252-272.
F. Dawalibi, D. Mukhedkar, "Multi-step analysis of interconnected grounding electrodes", IEEE Ttransactions, Vol. PAS -95, No. 1, Jan./Feb. 1976, pp. 113-119.
If you did attempt such a complex program, it should be tested extensively and verified before using it for a safety-lated application such as grounding design.
RE: Program for grounding analysis
I've already prepared a spreadsheet based on IEEE 80-2000, but it isn't sufficient for medium and large grounding grids.
I would like to write a prg, using the cymgrd results and the measuraments for testing it until I have the possibility.
Thank you for the suggestion of some papers
RE: Program for grounding analysis
RE: Program for grounding analysis
I will try
RE: Program for grounding analysis
IEEE Transactions on Power Delivery Jan 1997 pg 179 is limited to systems where soil is modelled in layers. The paper describes how to handle the 2 layer case. It relies in the developement of self and mutual inductances between grid elements.
Both algorithms can be done in Excell by writing a macro. I found the first one more generic because it is possible to model multiple layers (each layer is modelled by a rectangle of given resitivity that is much greater than the size of the grid) in addition to finite volumes such as rocks and ponds. I suppose the second paper can also deal with multiple layers but keeping track of all of the images becomes fearsome.
RE: Program for grounding analysis
RE: Program for grounding analysis
I have already developed by myself a software based on some pubblications. Starting from the resistivity measures and the Autocad drawing of the grid, I build the 2 layers soil model and then I can calculate:
the grid resistance, the GPR, touch and step voltage, profiles, touch voltage surfaces.
I tested it with good results, I could give you all the report of the comparison with the examples of IEEE80-2000 and with the results of CYMGRD.
Moreover I would like to compare my prg with the Gords' one
RE: Program for grounding analysis
RE: Program for grounding analysis
So I have compared the results of my prg with the measures. The prg is OK. The differences are negligible.
If a Client imposes a particular prg, I'm out. But it imposes only a Standard, I can propose my prg with the validation report.
RE: Program for grounding analysis
RE: Program for grounding analysis
The italian standard is very complex and requires expensive instruments. Only a few societies are able to do accurate measuraments.
RE: Program for grounding analysis
RE: Program for grounding analysis
I have analyzed two sample grids that you sent me by e-mail with the SES MALT program, for comparison with your Excel program.
Case 1:
0.5 m deep 50m x 30m grid in 2000 ohm-m soil, 8 meshes by 4 meshes. 0.01 m radius conductor. 1000A fault. Grid corners at (x=0, y=0), (x=50, y=0), (x=0, y=30), (x=50, y=30).
Grid resistance - 23.45 ohms
GPR - 23450V
Maximum touch voltage within grid area - 4900V directly over the four corners. Touch voltage inside grid at (x=2, y=2.5) - 4827V (other corners the same). Touch voltage at (x=-1, y=-1) - 8627V (other corners the same).
Maximum step voltage - 2856V at (x=0, y=7.5). Step voltage is about the same along the short sides close to cross conductors.
Case 2:
0.5m deep 18m x 12m grid in 300 ohm-m soil with a vertical cylinder of 50 ohm-m soil (10m diameter centered at x=0, y=0). Equal size 2 x 2 meshes. Conductor radius 0.005m. Grid corners at (x=2, y=0), (x=20, y=0), (x=2, y=12), (x=20, y=12). 1000A fault.
Grid resistance - 7.693 ohms
GPR - 7693V
Maximum touch voltage - 2370V at (x=17, y=9.5). Touch voltage in mesh closest to 50 ohm-m cylinder is lower (<2155V).
Maximum step voltage - 1309V at (x=20.5, y=6). Step voltage on side near 50 ohm-m soil is lower (<1178V).
How does this compare to your results?
RE: Program for grounding analysis
Case 1 used the formulation of self and mutual impedances between grid elements. I get the following:
Grid R = 23.9 ohms
Touch volts within grid = 5271
Touch volts at (-1,-1) = 9042
Vstep = 1818 volts in the same area as you noted (looks like I am way out on this value)
Case 2 was based on the first of the papers I referenced. I get 5.43 ohms for the grid resistance.
This same grid was modelled in the Transactions on power Delivery, July 2000 in a paper entitled "Analysis of Grounding Systems in Soils" where the result was 5.5 ohms.
My maximum touch voltage calculates to 4130 V at (10.5,0). My step voltage is 706V (from (11,0) to (11,2). The touch voltages within the low resistivity cylinder are about 10% lower than outside the cylinder. The touch voltage at (17,9.5) comes to 3690 V.
Again thanks for yout time. Not sure if I feel good or bad about the results.
RE: Program for grounding analysis
Addressing the original inquiry re CHEAP, there is http://members.aol.com/ocsoft/13.htm that apparently is an IEEE 80 and 142 grounding-grid DOS application for $550. I know nothing else about the material or firm offering it.
RE: Program for grounding analysis
RE: Program for grounding analysis
Case 1 results are very close. Case 2 is considerably different. I wonder why your touch voltage is much more than mine but your step voltage is much less. Your calculations are based on a paper written by the developers of the software I used, so the theoretical basis should be the same. I suspect either my input has an error (I will check), your input has an error, or your program has an error. This is the first time I have used a cylindrical soil model. One thing I note is that the calculation time is much longer. I calculated potentials every 0.5m over a surface extending 5m outside the grid (28m x 22m, about 2500 points). I didn't time the run, but it took well over 1/2 hour on a PC.
RE: Program for grounding analysis
You show maximum step voltages along the long edge of the grid (y=0). My results show maximum step voltages along the short edge (x=20). At (11,0), I get a step voltage of 184V. At (11,2) I get a step voltage of 371V.
RE: Program for grounding analysis
There is something stange about Case 2 firstly because our grid resistances are so far out ( published value = 5.5 ohms, myself=5.43 ohms, yourself=7.693 ohms). Based on such large differences, it isn't surprising our step and touch voltages are out. What is puzzling is, I think, based on what I know of the authors of the published paper, that you would be using the same software.
I note my greatest discrepancy lies in step voltage calculation while touch voltages are pretty close - Case 2 excepted. The program first calcuates the current in each of the grid elements. Then surface potentials are calculated at whatever spacing I want ( e.g. every 1m, .5 m, etc). From these values it is easy to calculate the touch voltage and step voltage by simple math operations ( i.e. subtraction) on the GPR and individual surface point voltages. Since my GPR's and touch voltages seem to line up pretty well with your results ( Case 2 excepted), I expect that my logic for calculating the element currents and surface potentials is acceptable. So why the larger errors in step voltage? I am thinking I may need to calculate surface potentials at a smaller increments.
Thanks for your time.
RE: Program for grounding analysis
The exaggeration may not be as great as apparent because the actual highest gradient may be at some angle other than between points (90° in my case). SES does have another method for calculating step voltages that calculates average gradients in any direction, but I usually don't use it because the first method is the default and step voltages are never a problem in practical cases anyway.
RE: Program for grounding analysis
RE: Program for grounding analysis
RE: Program for grounding analysis