MIL-HDBK-419A

When the step length is much less than the rod length, i.e., when

the step voltage can be approximated

as

(2-59)

The step potential can be expressed as a fraction of the ground rod potential as follows:

(2-60)

The fractional step voltages for ground rods of various length are given in Table 2-7. For this Table, rod

diameter is assumed to be one inch (2.54 cm) and the pace length is assumed to be three feet (0.91 m).

Table 2-7

Step Voltages for a Buried Vertical Ground Rod

Ratio of Step Voltage

Rod Length

To Electrode Potential

(Ft)

0.75

5

0.68

10

0.61

20

0.53

50

0.48

100

2-50