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 MIL-HDBK-419A
= 322 volts
This would be a safe value of step voltage for transients shorter than 30 milliseconds, if the transient, or surge,
impedance of the line does not greatly exceed its steady state resistance.
2.8.1.3 Minimizing Step Voltage. Table 2-8 lists several design approaches to reducing the potential hazards
of step voltage. The most effective method is the reduction of the resistance to earth of the earth electrode
system to as low a value as is economically feasible.
Table 2-8
Methods of Reducing Step Voltage Hazards
Remarks
Design Approach
Resistance to earth is directly proportional to soil
1 . Minimize resistance to earth of electrode
system.
Connection to earth electrode must be insulated to
2 . Bury earth electrode to reduce maximum
withstand 5 x
volts.
gradient on surface of earth.
Tends to equalize the surface potential over area of
3 . Bury a grid beneath the earth, surrounding
grid.
the earth electrode.
Fence must be grounded.
4 . Erect barricade so that personnel cannot
enter area of danger.
2-56
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