Unidirectional or Bi-directional TVS diodes - Which one to use?

[FreshmanNewbie]

I would like to understand in which places one should be using a unidirectional TVS diode and a bi-directional TVS diode.

In the USB power line, VBUS (5V), is it enough to place an unidirectional TVS diode? Or is a bidirectional TVS diode required?

Hence, can someone write an answer for clarification on where to use each one & which is better for what reason?

 

[FvM]

At first sight, bidirectional TVS are dedicated for AC respectively bipolar signals like RS232, DC power supply and unipolar signals should use unidirectional.