Earthing, is one of the most essential and critical aspects of electrical engineering but unfortunately in practise, also accorded the least importance and often neglected aspect.
It is common knowledge earthing system’s invariably are not installed in accordance with the requirements of the Local nor National nor International Codes of practise either through lack of knowledge, oversight, negligence or sometimes even knowingly.
Basic Facts about earthing systems are
1) The size and type of the electrode is driven primarily by the fault current.
2) The final earth pit resistance is a factor of the size of the electrode and more importantly the soil resistivity(ρ) and as a result there cannot be one solution for all applications.
3) The material of the earth electrode is not a factor in earth pit resistance
Formulae for Earth Pit Resistance ( R )
• plate earthing R = (ρ/4)* sqrt(π/2A)
• pipe earthing R = (ρ/2πL)* [ln(8L/d)-1]
• strip earthing R=(ρ/PπL)* [ln(2L2 /(wh))+ Q]