What is the maximum resistance allowed for the main earthing conductor?

The maximum resistance allowed for the main earthing conductor is set to ensure safety and minimize the risk of electric shock. A lower resistance in the earthing system allows for effective fault current dissipation, which is crucial for preventing dangerous voltages from appearing on equipment or conductive parts.

The value of 0.5Ω is therefore established as a critical standard. This limit ensures that in the event of a fault, the earth connection will effectively facilitate a protective device operation, such as an RCD (Residual Current Device), by ensuring a sufficient amount of fault current flows back to earth, allowing the device to trip quickly and enhance safety.

Therefore, the choice of 0.5Ω balances safety with practicality in installations, ensuring the earthing system works effectively within compliance standards while offering adequate protection against electrical hazards.