A method of locating a fault in a multi-terminal electrical power transmission scheme in which each terminal (T1, T2, T3, T4, T5, T6) is connected with a junction (11, J2, J3, J4) via a power transmission section and the or each junction (J1, J2, J3, J4) interconnects a plurality of power transmission sections , the method comprising the steps of: (a) measuring the voltage and current at each terminal (T1, T2, T3, T4, T5, T6); (b) calculating from the measured voltage and current at each terminal corresponding voltage and current phasors (V 1 , I 1 , V 2 , I 2 ); (c) determining from the calculated voltage and current phasors (V 1 , I 1 ) a synchronisation difference (Tp1, Tp2, Tp3, Tp4, Tp5) between the measured voltage and current at a designated terminal (T1) and the measured voltage and current at the or each other terminal (T2, T3, T4, T5, T6); (d) modifying the calculated voltage and current phasors (V 1 , I 1 ) to compensate for the or each synchronisation difference (Tp1, Tp2, Tp3, Tp4, Tp5); and (e) determining from the compensated voltage and current phasors (V TSyn , I TSyn ) the location of the fault, wherein the power transmission scheme is a multi-phase (a, b, c) power transmission scheme, step (a) of measuring the voltage and current at each terminal (T1, T2, T3, T4, T5, T6) includes measuring the voltage and current of each phase (a, b, c) at each terminal (T1, T2, T3, T4, T5, T6), and step (b) of calculating from the measured voltage and current at each terminal (T1, T2, T3, T4, T5, T6) corresponding voltage and current phasors (V 1 , I 1 , V 2 , I 2 ) includes converting the measured phase voltages (V abc ) and phase currents (I abc ) into respective phase phasors (V a , V b , V c , I a , I b , I c ) and then transforming the phase phasors (V a , V b , V c , I a , I b , I c ) into respective positive and negative sequence voltage phasors (V 1 , V 2 ) and positive and negative sequence current phasors (I 1 , I 2 ). (a) measuring the voltage and current at each terminal (T1, T2, T3, T4, T5, T6); (b) calculating from the measured voltage and current at each terminal corresponding voltage and current phasors (V 1 , I 1 , V 2 , I 2 ); (c) determining from the calculated voltage and current phasors (V 1 , I 1 ) a synchronisation difference (Tp1, Tp2, Tp3, Tp4, Tp5) between the measured voltage and current at a designated terminal (T1) and the measured voltage and current at the or each other terminal (T2, T3, T4, T5, T6); (d) modifying the calculated voltage and current phasors (V 1 , I 1 ) to compensate for the or each synchronisation difference (Tp1, Tp2, Tp3, Tp4, Tp5); and (e) determining from the compensated voltage and current phasors (V TSyn , I TSyn ) the location of the fault, wherein the power transmission scheme is a multi-phase (a, b, c) power transmission scheme, step (a) of measuring the voltage and current at each terminal (T1, T2, T3, T4, T5, T6) includes measuring the voltage and current of each phase (a, b, c) at each terminal (T1, T2, T3, T4, T5, T6), and step (b) of calculating from the measured voltage and current at each terminal (T1, T2, T3, T4, T5, T6) corresponding voltage and current phasors (V 1 , I 1 , V 2 , I 2 ) includes converting the measured phase voltages (V abc ) and phase currents (I abc ) into respective phase phasors (V a , V b , V c , I a , I b , I c ) and then transforming the phase phasors (V a , V b , V c , I a , I b , I c ) into respective positive and negative sequence voltage phasors (V 1 , V 2 ) and positive and negative sequence current phasors (I 1 , I 2 ). <EOS>