Hi,
How much noise we can apply in a system so that system keep remain in \alpha-homomorphic encryption. Otherwise after adding extra noise or increasing parameter values it will destroy the scheme.
Where \alpha belongs to {Somewhat, Partial, Leveled}.
In short what is the percentage handled by alpha.
Can you share any resource ?
Thanks in advance 
The answer depends on the scheme and performed computations (the “circuit”). For instance, in BGV/BFV/CKKS the highest noise is incurred for multiplications. The multiplicative depth determines how many multiplications can be performed in a series.
For a conceptual introduction to BGV/BFV, you can watch the following webinar: Homomorphic Encryption for OpenFHE Users – OpenFHE.org
If you are looking for a more advanced description of noise growth in BGV/BFV (for addition, multiplication, and other operations), I suggest reading Revisiting Homomorphic Encryption Schemes for Finite Fields