actually this ques was gives to me as an assignment in m.tech.. the full que. given by my teacher is:
"what are the a.c. sensitivity factors used in power system security analysis?how are they helpful in finding out Performance Index for voltage security?"
I am sorry, if you do not understand the question, or at least reword it in some other terms, then a, you can't answer it and, b I can't either. Go back to your lecturer and get him to explain it better.
Frank