What is the maximum allowable resistance for the ground wire

What is the maximum allowable resistance for the ground wire connecting the receptacles to prevent exceeding the safe current limit for microshock in the patient? Please show your work and explain your selection.

a) 75

b) 300

c) 0.5

d) None of the above. a) thru c) are too many ohms.

Solution

As resistivity of soil depends on moisture content. It\'s Resistivity changes throughout the year.

Therefore Earth resistance of a Installation in Minimum in Rainy Season and maximum in Dry season.

Although the Resistance Varies time to time there are some standard in the design of Ground wire.

They are

1 Maximum Allowable Earth Resistance for large power Station is 0.5 ohms.

2 Maximum Allowable Earth Resistance for major Station is 1ohm

3 maximum allowable earth resistance for Small power Station is 2 ohms

4 maximum allowable resistance for ground for other case is 5 ohms.

It\'s is to be noted that the Resistance between any point on the earthen body to the earth pit is less than 1 ohm.