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Program for grounding analysis
- Thread starter Alex68
- Start date
I rechecked the input for Case 2 and it is OK. The program segmented the conductors into 20 seperate segments. Total length of conductor 90m (18·3+12·3). You show a max touch voltage of 4130V at (10.5,0). This is at the bottom horizontal conductor 0.5m left of the middle vertical conductor. At this point, I get only 1069V touch voltage. The max touch voltage within the low resistivity cylinder and the grid is 2118V at (4,2.5).
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.
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.
jghrist
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.
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.
My step voltages may be exaggerated because the program uses the voltage gradient (V/m) between adjacent calculated potential points. I have calculated points every 0.5m. The maximum average gradient at a 1m step would be lower than the maximum gradient at a 0.5m step. If I use the average gradient of two 0.5m steps, I get a worst case step voltage of 1115V at (20.5,6) for Case 2 instead of 1309V. For Case 1, the difference is less than 1V because the gradient is fairly constant across the two worst case potential points. If you are averaging over more than one meter, you could be understating the maximum gradient at one meter.
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.
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.
pauletienne
Electrical
I am also looking for one excel spreadsheet to grounding calculation. Can you help me to find one free ? Thanks
pauletienne
Electrical
I am also looking for one excel spreadsheet to grounding calculation. Can you help me to find one free ? Thanks
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