This Book explain difficulties may facing the Distance protection for double circuit transmission line. All the simulation part is established and tested using Matlab environment and it contains three Special cases: 1)Distance Protection Performance Under Inter-circuit Faults On Double-circuit Transmission Line. 2) Investigation Of Faults On Busbar And Faults Near To The Distance Relay. 3) Investigate The Effect Of The Arc Resistance On The Operation Of The Impedance Relay Protection.