Digital Ground Resistance Tester Model 4500
17
4.1.1 Effect of Ground Electrode Size and Depth on
Resistance
Size:
Increasing the diameter of the rod does not materially reduce its
resistance. Doubling the diameter reduces resistance by less than 10%.
0
25
50
75
100
1/2
5/8
3/4
1
1 1/4
1 1/2
1 3/4
Rod Diameter (inches)
Resistance in %
Figure 5
Depth:
As a ground rod is driven deeper into the earth, its resistance
is substantially reduced. In general, doubling the rod length reduces the
resistance by an additional 40%.
5
15
25
35 40
50
60
70
1
2
3
4
5
6
8
10
20
30
40
60
80
100
200
Driven Depth in Feet
Ground Resistance Versus Ground Rod Depth
Resistance in Ohms
1/2" dia.
1" dia.
Figure 6
Содержание 450.100
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