The Earth electrodes should be designed to withstand the fault current without any physical damages. The fault current carrying capacity of a material mainly depends on cross sectional area of that particular material. In this article, we shall discuss about the current carrying capacity of pipes and strips of different dimensions and different materials as specified by IS 3043:2018.
In general, the amount of electric current flowing per unit cross sectional area of a material is called current density of a material. The current density of the earth electrode can also be calculated by the formula specified in IS 3043,
Where,
S = Cross sectional area, in mm²
I = value of fault current, in Amps
t = operating time of disconnecting device, in sec
k = factor dependent on the material of the protective conductor, the insulation and other
parts, and the initial and final temperatures.
For the specific cross sectional area, the current density can be calculated from the above
formula. These values are applicable only for disconnection times not exceeding 5 sec.
Cross sectional area of pipe,
Initial temperature: 40 ͦC, Final temperature: 500 ͦ C
R.M.S current density k for steel at given temperature= 80 A/ mm²
Note: These values are specified in IS 3043.
From the above calculations based on IS3043:2018, we can conclude that the fault current
carrying capacity mainly depends on cross-sectional area and the material of the electrode.
