A new pilot protection principle based on fault component integrated impedance of transmission line with thyristor controlled series capacitors(TCSC)and thyristor controlled reactor(TCR)is proposed. The fault component integrated impedance becomes a ratio of the sum of the fault component voltage phasor to the sum of the fault component current phasor of two terminals. It is used to identify if a fault exists on the line. If the fault is out of the line

the calculation value of fault component integrated impedance reflects the line capacitive impedance with a greater amplitude; if the fault is on the line

it reflects the system impedance and line impedance with a relatively smaller amplitude. According to the amplitude of the fault component integrated impedance

the fault location can be distinguished. The new principle relays can be set easily and has phase selection capacity

which gets free from the influence of capacitive current and TCSC and TCR

and resists the higher fault resistance. The effectiveness of the new principle is validated by dynamic simulations of the northwest 750 kV system model.