CT working principle

Here is one attempt, among many others from Googling "current transformer".

Tornado,

I think in some place, Google is like some martian civilisations which they have not heard of .

There are some places where Google (or Wikipedia) is restricted, but I suspect the OP has access to them. Their explanations are usually better than forum answers, and should be tried first. Then, if something seems unclear or complicated, a forum like CR4 is a great place to go next--but by then armed with some basic knowledge.

Looking at his previous post the phrase "lost cause" springs to mind.

A current transformer's primray winding is connected in series with the load. When a load current flows through this winding, it sets up an alternating magnetif flux in the core of the CT; when this flux cuts the secondary winding conductors, an EMF is induced in the secondary winding conductors following Faraday's Laws of Electromagnetic Induction. The magnitude of this induced EMF is directky proportional to the rate of change of flux and the number of turns in the secondary winding. When you connect a load or burden to the CT Secondary winding, a current starts flowing in the secondary winding thro the load connected to the secondary. Adn, as the EMF induced in the secondary is proportional to the flux, which in turn is proportional to the primary current, when the primary current varies, so will be the flux, the induced EMF in the CT secondary and thus the secondary current too.