Usage of semicolon

I have never used semicolons in any of my technical and non-technical writing so far. Probably, today I felt the urge to know about its importance. After some Internet digging, I found usage of semi-colon can be summarized by three points.

(i) Seperate two independent yet closely related clauses.
My first day in army was nerve-breaking; the colonel seem to observe every move that I make.

(ii) two clauses seperated by a conjunction
It seems I'm running late; perhaps I have to go now.

(iii) Seperate semicolon when items in a series contain commas
She had lived in Mumbai,India; Colombo, Srilanka; and Canberra, Australia.