Can you help me on Earth Mat designing of a Electrical Sub-station under the following points-
A>Procedure of designing of a Earth Mat.
B>Materials used in designing.
C>Benefits of Earth Mat in a Electrical Sub-Station.
C>Rating of Earth Mat (if any).

Vivek,

This is just the type of "challenging opportunity" that you should be researching yourself, there are plenty of interesting papers available for the price of a Google search. And best of all you can seek results specific to the locale you're in, something which only you know (and the practices vary widely).

Alan

Please go through IEEE Std-80. And good luck.

Best guide on the subject is the book, "IEEE Standard 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems, and it was last revised in 1991".
I prefer to call "Earth Mat" as "Ground Mat". Criterion for selection of material for grounding mat is that it should be cost effectively a good electrically conducting medium, while simultaneous it should be such that it remains reasonably protected from aqueous corrosion of expected life time.

Thanks to David Haizelden sir, Anand kumar gupta Sir,Navdeep sir & Alan Maltz sir
for your valuable advice and help.Thanks a lot.

Vivek,

About the year 1982, I have completed the design of the ground mats of 2 major substations for a US military base in Korea. At that time I used the IEEE Standard for Ground Mat design and I did it using manual calculations. It was laborious but very challenging.

About the year 1990, I was able to use a cheaper software for my design of a standard utilty substation in the US, Maryland. It was a great software tool I got from "Orloff". Try to find it. Nowadays there are many other expensive softwares in the market like SKM, ETAP, etc, but the Orloff version was very user friendly and pragmatic one.