Calculation of Resistance to Ground:Two Ground Rods:Spacing between rod is shorter than length of rod.

Calculation of Resistance to Ground:Two Ground Rods:Spacing between rod is shorter than length of rod.

1Ground resistivity:ρΩ・mSee below table.
2Length of vertical ground rod:Lm-
3Radius of vertical ground rod:amm-
4Spacing between two rods:sm. L>s-
5GraphPlot Input Data: , Figure:
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Keyword・Reference・Remarks・History

LaTex


Markup:R=\frac{\rho }{4\pi L}(\log_{e}\frac{4L}{a}+\log_{e}\frac{4L}{s}-2+\frac{s}{2L}-\frac{s^{2}}{16L^{2}}+\frac{s^{4}}{512L^{4}}\cdots )

Keyword

Resistance to Ground,Two Ground Rods,Spacing between rod is shorter than length of rod,Ground resistivity,Length of vertical ground rod,Radius of vertical ground rod.

Reference

[1]:H.B.DWIGHT:『Calculation of Resistances to Ground』,American Institute of Electrical Engineers,1936,Volume: 55 Issue:12,pp.1319 - 1328.
[2]:Copper Development Association:『Earthing Systems - Fundamentals of Calculation and Design』,pp.2

Remarks

・ρ:Ground resistivity(Ω・m).Cited from Reference[2].
Type of Ground Range of values Average value
Boggy ground 2 - 50 30
Adobe clay 2 - 200 40
Silt and sand-clay ground, humus 20 - 260 100
Sand and sandy ground 50 - 3,000 200 (moist)
Peat >1,200 200
Gravel (moist) 50 - 3,000 1,000 (moist)
Stony and rocky ground 100 - 8,000 2,000
Concrete: 1 part cement + 3 parts sand 50 - 300 150
1 part cement + 5 parts gravel 100 - 8,000 400
・R:Resistance to Ground
・L:Length of vertical ground rod
・a:Radius of vertical ground rod
・s:Spacing between two rods
・Making above Equation Image is powered by CODECOGS

History

・2010/08/14:Upload

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