Please do some more literature survey. Please collect the material from IEEE, RG, Google etc. Also refer to latest standard books.You are from a premiere institute. you can easily download lot of papers, PPTs and tutorials just by giving a few key words of your problem.
@Krishnarayalu Thanks for your answer. I would definitely explore literature surveys, etc.
I have a quick question: In IEEE Bus data, it can be seen that for some bus transformer turns ratio is 0 at some buses. That is intuitively contradictory. It should not be zero at all.
Here is the link for the data: http://www.ee.washington.edu/research/pstca/pf14/ieee14cdf.txt
It is valid point that transformer turns ratio can not be zero. Normally range is between 0.9 and 1.1. That is how suggestion has been given to choose 0.9 or 1.1. But from the data it can be seen that there are thre transformers whose values have been specified, if I have got it right. Where we have no specification on actual tapsetting it is customary to take it as 1.0 only.