Lighting and Earthing System

Question

How do you design earthing system for example a small power plant of about 2MW. How do you select electrodes? Are the electrodes installed above or below grade? What eventually takes the fault current in the ground?

When can one make use earth rods?

Kindly differentiate between earth electrode and earth rod with regards to usage. Can you connect an earth rod to an electrode?

Answer 1

Soil resistivity is the main domain in earthing system design, most petrochemical industry require 1 ohm for the earthing system, this can be achieved either by earth grid or earth wells, if the electrode is meant for cathodic protection, then no that is not allowed , but if that is for earthing purposes then yes can be used  

Answer 2

The soil condition determines what kind of, and how many electrodes,

(rods, plates, wire loop,etc.), is /are used.

The purpose of the electrodes is to connect the wired grounding

system

to the earth.

The resistance of the concentric 'shells' of soil around the electrodes

is a design parameter for the system.