Understanding Symmetrical Components

This should help....

http://www.mantatest.com/symmetrical-components-made-easy-part-1/

A1) Until such moment as the circuit protective device(s) operate(s), the primary current will be such multiple of the secondary current as is determined by the turns ratio of the transformer subject the core not being magnetically saturated. The current in the primary transmission line is the same as the current in the windings as the former is supplying the latter.

A2) As A1.

A3) It depends upon the nature of the fault. Generally, in a correctly-designed system, the circuit protective device(s) operate(s) before any significant damage is done.

A4) There will be a short-term increase as the motor stalls, then the circuit protective device(s) will operate, disconnecting the motor; from this point the current on the particular motor circuit falls to zero.

It would be interesting to know what you mean by "...complex mathematics..." since the word "complex" has multiple meanings in power engineering. Unfortunately Symmetrical Components is both complex and requires complex math, so learning vector math will assist in your understanding of the topic.

Fortunately the specific questions that you asked are standard situations that are covered in most good power engineering texts and handbooks, where they are derived and presented in (mostly) algebraic fashion. One thing to be wary of are blogs, they are often rife with misinformation (CR4 included), get a well respected textbook (Blackburn or Stevenson) that is at your current educational level. The topic is over a hundred years old, and used to be solved on a slide-rule, so you can learn it too.

Excellent