Question

if a woman is using a copper-t, will it help in protecting her from sexually transmitted diseases

Answer 1

No copper-t cannot help in protecting one from sexually transmitted diseases
 

Answer 2

The copper-t or copper IUDs (Intrauterine contraceptive devices) will not help in the protection from STDs (sexually transmitted diseases) as, it only has the function of bringing a local antinfertility or infertility effect by bringing up the action to the release of toxic cytokines.
Since, they have ionised copper which slowly diffuses at the rate of some 50 micro grams per day it will work effectively to make the eggs unfertilised or to not release from the ovary (to undergo a multitude of changes) at all.
There are also various models to adjust the uterine wall depending upon the square Millimeter of having copper loaded onto it such as, Cu T 200 is one of its kind.