After trying out various suggestions from all of you, it turned out that one port of the surge protector ( with 8 ports, call it say SP-1 ) had grounding problem. I had plugged another surge protector ( Call it SP-2 ) into that port of SP-1 & had plugged 7 monitors & CPU into SP-2 which caused grounding problem in 7 monitors & Main chassis.
I changed the port & it solved the problem. Still I called the electrician to check all wiring. He put in extra grounding in main supply & problem is gone. But I can't understand how grounding problem could give such a strong electric shock.
I sincerely appreciate the suggestions from all of you & am very grateful.