Normally, we just use the CTT (CT test terminal) for shorting the 2nd circuit for maintenance the relay or meter. However, as like the attached circuit in number 1, sometimes we use the CT the shorting terminal block (STB-P in the drawing and attachment 2) and the CTT (CTT-P in the drawing and attachment 3) at the same time. Why use the CT shorting block even there is a CT test terminal already?
