A phase pilot protection of transmission line based on the voltage difference between both terminals is proposed. According to the angle characteristics of the individual phase impedance
the phase value is evaluated by the ratio of the two equivalent differences of the fault-superimposed components of voltage at each phase of the line
then whether the fault occurred in the protected region is judged. When the phase values just equal to 0°
the fault appears outside of the protected zone
and the fault is inside of the protected zone when they equal to 180°. The proposed protection with identity of sensitive operation and adaptation is capable of resisting the line capacitors
and can be directly used in pilot protections of most transmission lines without compensation. The EMTP simulation and the dynamic simulation show the effectiveness.
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