Question

For a specific wiring in a building, the full load current is 10 A. what will be the maximum permissible leakage current?
1. 0.008 A
2. 0.002 A 
3. 0.005 A
4. 0.003 A

Answer 1

Correct Answer - Option 2 : 0.002 A 

Concept:

Full Load Current(I_FL): A full load current is a maximum current that electrical equipment is designed to carry under rated conditions.

Leakage current(I_lek): A leakage current is an electric current in an unwanted conductive path under normal operating conditions.

Note: According to IE Rule 48, the maximum permissible value of leakage current should not be exceeded beyond the \(\frac{1}{{5000}} \) times of full load current.

Insulation Resistance(IR): An insulation resistance (IR) is the total resistance between any two points separated by electrical insulation.

It is given by,

\(IR = \frac{{Supply\;Voltage}}{{{I_{lekage}}}}\)

Note: IR of a cable is also given as:

\(IR = \frac{\rho }{{2\pi l}}{\log _e}\frac{{{r_2}}}{{{r_1}\;}}\)

Where ρ is the resistivity of cable on Ωm

l is the length of cable in the metre.

r₁ is the radius of core in metre

r₂ is the radius of cable in metre

Calculation:

Given, I_FL = 10 A

According to IE Rule 48:

\({{\rm{I}}_{{\rm{lek}}}} = \frac{{{{\rm{I}}_{{\rm{FL}}}}}}{{5000}} = \frac{{10}}{{5000}} = 0.002{\rm{\;A}}\)