This　paper　analyzes　the　characteristics　of　equivalent　dynamic　power　frequency　impedance　of　the　thyristor-controlled　series　capacitor　(TCSC)　and　the　integrated　impedance,　which　is　defined　as　the　ratio　of　the　sum　of　the　voltage　phasors　across　the　two　ends　of　the　transmission　line　to　the　sum　of　the　current　phasors　through　the　two　ends　of　the　same　transmission　line.　The　integrated　impedance　of　the　transmission　line　is　used　to　determine　whether　there　is　a　fault　inside　the　protected　line　section　or　not.　When　an　external　fault　occurs,　the　integrated　impedance　reflects　the　capacitive　impedance　of　the　protected　line,　its　imaginary　part　is　negative,　and　the　absolute　value　of　its　imaginary　part　is　large.　When　an　internal　fault　occurs,　the　imaginary　part　of　the　integrated　impedance　on　the　fault　phase　is　either　a　positive　value　or　a　small　negative　value.　According　to　such　characteristics,　internal　faults　can　be　distinguished　from　external　faults.　Based　on　integrated　impedance,　a　novel　pilot　protection　scheme　for　the　transmission　line　with　TCSC　and　controllable　shunt　reactor　is　presented.　Digital　simulations　based　on　750-kV　transmission　systems　show　that　the　presented　scheme　offers　high　sensitivity　and　reliability　with　many　advantages　over　conventional　current　differential　protection.