### Earthing conductor size calculator:

Earthing conductor is used to carrying the electrical fault current to the ground. Here our earthing size calculator is used to calculate the exact required earthing conductor size in sqmm.

Enter the fault current in kilo Amps and fault clearing time in Sec. Then press the calculate button to get the required earth conductor size in Sqmm.

### Earthing conductor size calculation Formula:

Earth conductor size PE_{(Sqmm)} in sqmm is equal to the square root of maximum operating time t_{(S)} in Seconds times of fault current square I_{(fault-A)} divided by material constant k. Hence we can write the formula for finding earth conductor size as below,

Earth conductor size PE_{(Sqmm)} = **√** (I_{(Fault-A)}^{2} x t_{(s)}) / k

Material |
Material Constant (k) |

GI | 80 |

Copper | 205 |

Aluminium | 126 |

But by considering Safety factor as 1.5,

Earth conductor size PE_{(Sqmm)} =1.5 x **√** (I_{(Fault-A)}^{2} x t_{(s)}) / k

Here safety factor is your choice,

**Example:**

Let we calculate the required GI earth conductor size for 20kA Fault Current at 0.5 sec.

Use our formula,

Earth Conductor size = **√ **(20000^{2} x 0.5) / 80

= 20000 x 0.707 / 80

= 176.8 Sqmm

Approximately 185Sqmm.

Generally, GI is availed in the busbar structure hence Or You can take any combination of conductor size such as 50×3.5 Sqmm or 25x8Sqmm etc.

However, the size of the conductor is above the resultant size.

according to your calculator the earthing conductor size for 50 KA Fault is about 250 mm2

but when using Etap with the same values it give 150 mm2

Load calculation in the earthing cable size short formula

Cu

GI

Alu