Program for grounding analysis

[strongone]

I am currently working on a prg to perform grounding analysis of earthing grids. I am using the work by R.J Heppe “Computation of potential at surface above an energized grid or other electrode, allowing for non-uniform current distribution”, IEEE Trans. on Power App. and Sys., 98, 1978-88.

this theory cant model the effects of ground rods on the grounding system and i am having some difficulty modeling grids that contain conductors that are at angles other than 90 and 0 degrees i.e triangular grids,... how can i overcome these problems aslo how can i verify my results?? i know Alex68 had a similar thread, but i just need to clear up these issues

 

[Alex68]

strongone,

I based my work on the following papers:

1) Chow, Elsherbiny, Salama, "Efficient computation of rodbed grounding resistance in a homogeneous earth by Galerkin's moment method", IEE Proc.-Genr. Transm. Dirstrib., Vol. 142, No. 6, November 1995, page 653-660

2)Elsherbiny, Chow, Salama, "A fast and accurate analysis of grounding resistance of a driven rodbed in a two-layers soil", IEEE Trans. on Power Delivery, Vol. 11, No. 2, April 1996, pages 808-814

3) Chow, Elsherbiny, Salama, "Surface voltages and resistance of grounding systems of grid and rods in two-layer earth by rapid Galerkin's moment method", IEEE Trans. on Power Delivery, Vol. 12, No. 1, January 1997, pages 179-185

Starting from the theory summerised in these papers, I developed a prg for the calculation of the earthing resistance, step and touch voltage profiles, 3D surface of touch voltage, for grounding grids of a generical shape and drawn with Autocad.
I validated the prg comparing it with the examples contained in the IEEE80-2000 and with the results reported in the manual of the popular CYMGRD. I prepared a report of this validation.
I am ready to share with you my experiences and to send you the report.

 

[strongone]

I was shying away from this algorithim not because it deals with self and mutual resistances but it seems that it cannot calculate the mutual resistance bewteen angled (other than 90 and 0 degrees) conductor segments.
Currently I am using the Neuman Integral to calculate self and mutual resistances between segments, as it accomodates conductors angled conductors. However I am sceptical of the results obtained for the mutual resistance between non-coplanar , perpendicular conductors(i.e ground rod and horizontal conductor).

The only difference between our methods is the resistance calculation between condutors, thus I welcome your input

 

[jbartos]

Suggestion: The triangular grid resistance might use relationships from the cube having a resistance in each edge, side diagonal, body diagonal and potentially a total resistance of the cube between edge points.

 

[Alex68]

The calculation of the mutual resistance between angled segments is very difficult with the Galerkin's moment method. It implies that you solve very difficult integrals.

I found a very simple but working solution: ONLY to calculate this kind of mutual resistance, I substitute the segments with spheres placed in the middle points of the conductors!

You could say that it is a dangerous semplification, but it works very well. The error in the calculation of the grounding grid resistance is less than 2% to 4%, compared to other prgs. I say that it is acceptable considering the approximations in the soil resistivity measuraments and the soil model.
On the other hand I calculate the correct integrals for the surface voltage.

Suggestions:
1) remember to subdivide conductors into segments at each intersection
2) add spheres at the ends of the segments in order to obtain a correct surface voltage trend
3) pay attention with the image conductors when considering a two layers soil model

 

[rezaa]

Alex:

I will appreciate you to let me have your report as well.

reza_588@yahoo.com

 

[strongone]

Alex68:
I am having problems determining the mutual resitance between two perpendicular conductors. Your third reference states that
one integral can be determined analytically and the other by Gaussian quadrature of third order. Could i send you my solution and correct me where i am wrong? ziax@tstt.net.tt

 

[Alex68]

rezaa:
I have already sent you the report. Please let me know your opinion.

strongone:
I'm sending you an email. I will be pleased to try help you as I can.