You will be able to find the answer to the following questions from this document:

What is the purpose of a substation earthing system?
What is the maximum allowable resistance to earth for a substation earthing system?
How are earth rods installed?
What is the purpose of equipotential bonding in a substation?
What are dedicated ("clean") earth systems, and why are they used?
What type of testing is required for a substation earthing system?
What information should be included in the Operation and Maintenance (O&M) Manual regarding the earthing system?
What is the maximum allowable resistance to earth for the complete earthing system as per the document? How is this resistance achieved during installation?
Explain the difference in connecting HV equipment to the earthing system when there is an external HV earthing system versus when an independent earthing system is provided.
When are earth mats used instead of earth rods? What are the material options and placement requirements for earth mats?
Explain the purpose and material options for inspection pits in the earthing system.
Detail the conductor material, connection method, and labelling requirement for connecting earth rod electrodes.
What are the requirements for the material, dimensions, and mounting of earth bars?
Describe the specific workmanship requirements for connecting earth rod electrodes, including the depth, spacing, and connection methods.