Limited Point Grounding System - ADInstruments AD6412 Manual De Usuario

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figure below:
Where: R is the target grounding resistance.
1
R is the equivalent resistance of the other entire tower grounding resistances
0
paralleled.
Although strictly on the theoretical grounding, because of the existence of so-called
"mutual resistance", R
(slightly higher than its IEC parallel output value). But because a tower-grounding
hemisphere was much smaller than the distance between the towers, and with a great
number of locations after all, R
assume R =0 from an engineering perspective. In this way, the resistance we measured
0
should be R1.
Times of comparing tests in different environments and different occasions with the
traditional method proved that the above assumption is entirely reasonable.

2. Limited Point Grounding System

This is also quite common. For example, in some towers, five towers are linked with each
other through overhead ground wire; Besides, the grounding of some of the buildings is
not an independent grounding grid, but several grounding bodies connected with each
other through the wire.
Under such circumstances, the above R
results of the measurement.
Due to the same reasons mentioned above, we may ignore the impact of the mutual
resistance; and the equivalent resistance of the grounding resistance paralleled is
calculated by the usual sense. Thus, for the grounding system of N (N is smaller, but
larger than 2) grounding bodies, it can offer N equations:

R
1
1
R
R

2
1
R
1
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R R
1 0
is not the usual parallel value in the sense of electrical engineering
0
is much smaller than R
0
1
R
1T
1 1
......
  
R R
2
3 N
1
R
2
1 1 T
......
  
R R
3 N
Manual de usuario AD6412
. Therefore, it can be justified to
1
regarded as 0, will yield more error on the
0
AD Instruments
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