12
below.
Figure 4
Then R
T
=R
x
+ R
0
Of which:
R
T
: the measured value;
R
x
: grounding resistance;
R
0
: All other tower grounding resistance of the equivalent
parallel resistance.
Although from a strictly theoretical, because of the so-called
"mutual resistance" existence, R
0
is not the usual sense
electrotechnics parallel value (it will larger than the value in
electrotechnics), but because the grounding hemisphere is much
less than their distance and number of the grounding points is big
so R
0
will be much less than R1 and we can assume R
0
= 0. Then
R
T
≈ R
x
.
The theory is proved be true with many test under different
environments comparing to traditional method.
Non-contact measurement method (i.e., double clamp) is an
advanced measurement technology and it has many advantages.
However, the measure resistance includes the he entire circuit
grounding resistance. Care must be taken in analyzing the result.
