1. The document validates the grounding software Aspix by comparing its results to sample calculations in IEEE 80-2013. 2. For a uniform soil example, Aspix results deviated from IEEE 80 by less than 16% for all values except step voltage, which deviated 16%. Deviations from another program were less than 4%. 3. For a two-layer soil example, Aspix results deviated from IEEE 80 by less than 6% for all soil conditions tested.

1. Aspix Validation
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IEEE 80 Aspix Validation
IEEE 80-2013 standard has several sample calculations, which serve to validate the grounding software.
Annex B has five examples of calculation of grounding grids in uniform soils and one example of calculation in
two-layer soil. Annex F has the results of different arrangements of grounding systems in two-layer soils, for
various reflection indexes. To test the Aspix program, the Example 2 of Appendix B (page 135) and the SR9 case
of Appendix F (see table F.2, page 186) have been chosen.
1. UNIFORM SOIL VALIDATION
Figure 1 shows a plan view of the grounding grid of Example 2 of Annex B. This grounding grid is a 70 m x 70 m
grid with 20 vertical rods, each 7.5 m long, around the perimeter of the grid.
Figure 1. Example 2 - Annex B – Plan view
The design data are shown in Table 1. The calculated GPR for this case is 5247 V.
Table 1. Input data for Example 2 - Annex B
The grounding grid resistance is calculated as follows:
The program of EPRI TR-100622 gives a result of 2.52  for the grid resistance.

2. Aspix Validation
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The step voltage is calculated as follows:
The program of EPRI TR-100622 gives a result of 459.1 V for the step voltage.
The touch voltage is calculated as follows:
The program of EPRI TR-100622 gives a result of 756.2 V for the touch voltage.
Figure 2 shows the plan view of the grounding grid simulated in Aspix.
Figure 2. Example 2 - Annex B - Aspix grounding grid plan view
Table 2 shows the simulation results. Aspix gives results of 2.488 , 784.63 V and 462.56 V for the grid
resistance, touch voltage, and step voltage, respectively.

3. Aspix Validation
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Table 2. Example 2 - Annex B - Aspix results
Table 3 shows the comparison between IEEE 80 (using equations), the EPRI TR-100622 program and Aspix
results and Table 4 shows the percentage deviations.
Table 3. IEEE 80 and Aspix results comparison
IEEE 80 EPRI TR-100622 Aspix
Resistance 2,75 2,52 2,488
Touch voltage 747,4 756,2 784,63
Step voltage 548,9 459,1 462,56
Table 4. Percentage deviation of the Aspix results
Deviation IEEE 80 Deviation EPRI TR-100622
Resistance 9,5 % 1,2 %
Touch voltage 5 % 3,8 %
Step voltage 15,7 % 0,63 %
As shown, the deviations are very low except for step voltage, in which the deviation of Aspix results respect to
IEEE 80 is 15.7%; however, in this case the deviation of Aspix respect to EPRI TR-100622 program is very low
0.63%, so the Aspix results are considered valid.
2. TWO-LAYER SOIL VALIDATION
Figure 3 shows a plan view of the grounding grid of SR9 case of Annex F. This grounding grid is a 20 m x 20 m
grid with 9 vertical rods, each 10 m long. The asterisk symbol (*) shown in the figure indicates the point where
the maximum touch voltage is obtained.
Figure 3. SR9 Case, Annex F – Plan view

4. Aspix Validation
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The top layer has a resistivity of 100 m and the resistivity of the lower layer depends on the reflection factor K.
In this case, the touch voltages are given as a percentage of GPR. Table 5 shows the results given by the
IEEE 80.
Table 5. SR9 Case, Annex F
Figure 4 shows the plan view of the grounding grid simulated in Aspix.
Figure 4. Grounding grid plan view - SR9 Case, Annex F - IEEE 80
The reflection factor k is given by the expression:
12
12




k
Where 1 and 2 are resistivity of the upper layer and lower layer respectively. Table 6 shows the cases
simulated in Aspix.

5. Aspix Validation
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Table 6. Case SR9 Annex F - Simulated cases
Reflection factor k Upper layer resistivity 1 Lower layer resistivity 2
0 100 m 100 m
0,5 100 m 300 m
-0,9 100 m 5,26 m
Table 7, Table 8 and Table 9 show the Aspix results for the cases simulated.
Table 7. Case SR9 Annex F - Aspix results, k = 0
Table 8. Case SR9 Annex F - Aspix results, k = 0,5

6. Aspix Validation
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Table 9. Case SR9 Annex F - Aspix results, k = -0,9
Table 10 shows the comparison between IEEE 80 and Aspix results and Table 11 shows the percentage
deviations.
Table 10. IEEE 80 and Aspix results comparison
k = 0 k = 0,5 k = -0,9
IEEE 80 Aspix IEEE 80 Aspix IEEE 80 Aspix
Resistance 1,81  1,768  3,5  3,48  0,164  0,162 
Touch voltage 21% 21,18% 13,4% 13,69% 35% 37%
Table 11. Percentage deviation of the Aspix results
k = 0 k = 0,5 k = -0,9
Resistance 2,3% 0,6% 1,2%
Touch voltage 0.9% 2,2% 5,4%
As shown, the deviations are always less than 6%, so the Aspix results are considered valid.