What will happen current transformer connected in parallel?

If current Transformers are connected in parallel, they will superpose and supply a high current.

EDIT:

I suppose you drive the transformer with a voltage source.

By the way, it depends how you connect the transformers:

A - primary side in parallel and two independent loads at the output

B - primary sides in parallel and secondary sides in parallel

Say turns ratio is Np:Ns, then for each transformer you have

Vp/Np=Vs/Ns, Np*Ip=Ns*Is.

IE If Np=N, Ns=1, you have a voltage step down transformer

(Vs=Vp/n, Is=N*Ip)

A: You will impose the same secondary voltage to each load, that is Vs=Vp/N.

Input current is the sum of each output load multiplied by transformer turns ratio. If the two transformers have M and N turns ratio, you have Iin = M Is1 + N Is2 (Is1=Is2 only if loads are identical)

This architecture is used in modular / redundant systems.

B: Theoretically, it's like having a single transformer. In practice, I have never seen it. What you do is to split the current in two different cores, so that your losses will be lower for each core. That *could be handy if you wanna use ferrites which are undersized for your application and you don't want to buy a new one.