Calculation and concept of ground resistance

The ground resistance is resistance from the earth electrode (earth electrode) to deep in the earth.

Calculation of ground resistance

  The ground resistance is requested from the resistivity of the soil by the calculation, and of what character one the ground resistance is is seen.
  The resistivity of the soil  About 10-1000[ Ohm*m]  It is about 100[ Ohm*m] in and a usual soil.

Diffusion of earth current to the earth

The earth is given to a hemisphere center with pattern diagrams of a left earth ohmeter calculation, and respect on the hemisphere is made a ground level.   The point on the hemisphere is thought to be a flow of an equal anywhere current by the current's that flows from the earth of the center diffusing to the earth in all directions when assuming the one with uniform anywhere electric character of the soil. Therefore, the point on the hemisphere is thought that potential is all equal. There is not an influence electrically even if the point where potential is equal is connected with the lead mutually either. Therefore, you may think this hemisphere surface to be a thin conductor.   r[m] and the surface area S[m2] : this hemisphere radius half of the ball.   S = 2 * 3.14 * r2

Calculation of ground resistance by integration

  Is it minute thickness in this hemisphere surface?This thickness assuming that the soil of has adhered?Resistance ? Hacana only of soil of dR [Ohm]  It is p of the soil of ..peel.. , as for the resistivity. p [Ohm*m]  Then,

  dR = p*dr/S

It becomes like expression 1 in a word. The ground resistance becomes the one that this expression 1 was added from the range to infinity where it is. That is, it will only have to integrate expression 1.

If the radius integrates the resistance of the soil of minute thickness that adheres to this hemisphere from an infinite smallness to infinity, the ground resistance becomes infinity.   Therefore, this hemisphere radius decided to be integrated from a[m] of limited to infinity. Calculably as expression 2 of ground resistance R when domed of a[m] in the radius risks the earth pole in a word.

  This result
  R = p/(2*3.14*a)      - - -Expression 3

Calculation result of ground resistance in domed earth pole

A left graph is a calculation of the ground resistance in a domed earth pole by expression 3.   From this graph to P=100[ Ohm*m] level of unquestionable in the following resistance of hemisphere radius 5m-10m or more even if it becomes 1.6 Ohm-3 Ohm or less and it disregards itIn a word, the ground resistance is to decide in the state within 5-10m in radius. (50-100m or more in radius in P=1000[ Ohm*m])   It is enlarged that it can be only an earth electrode (earth electrode) or when the earth electrode surrounding is made a material that electrifies it easily, it is possible to lower the ground resistance.   The ground resistance is to depend on the radius resistivity of the soil in the hemisphere within about 10m and the size of the earth pole greatly.

  The size of the earth pole to do can be presumed to the value of a necessary ground resistance from the graph ..on... For instance, to obtain the ground resistance below 100 Ohm, it is understood to only have to make the one more than the equal to the hemisphere of 1.5m in radius an earth pole in P=1000[ Ohm*m]. In a word, it is understood to have to drive the earth stick of 1.5m or more in length within the range of 3m or more in diameter how many it is.

Method of reducing ground resistance

• The electrode of the earth (earth) is enlarged as much as possible.
• The electrode of the earth (earth) is buried as deeply as possible.
• These the plural are connected in parallel by setting up the earth (earth) in a place away from the electrode of the earth (earth) by ten meters or more.
• Charcoal, salt, and earth resistance decrease medicine that conducts electricity easily to soil in the vicinity of earth (earth) electrode  ..(.. brand name  Athlon, San earth, Dordencret, Ticorgel, Amolars, and Nippiars etc.)  The resistivity of the soil is lowered mixing.
• The ground resistance can be reduced further if these methods are combined and it does.