The study of this book is focused on investigation and simulative testing of differential protection of transmission line with effective elimination/reduction of errors due to saturation of current transformers. A small introduction of power system and faults with transmission line along with the discussion of current transformer errors and corrections. And further in details; The study and investigation on Line Differential Protection insensitive to CT saturation containing Preparation of suitable power system model in ATP-EMTP for simulative studies, Analysis of operation of differential protection for internal and external faults. Preparing a protection algorithm (Scripted in MATLAB) with respect to CT saturation effects, Testing of proposed solution with EMTP-generated and recorded faults cases and final draw of conclusion.