Focusing on the operating mode of series compensation capacitors being at the end of transmission lines， this paper defines the terminal calculating voltage between the location of the protective relay and the series compensation capacitor as the compensation voltage. Then the characteristics of the compensation voltage are analyzed in the events of the fault location is before and behind the series compensation capacitor respectively. When the fault location is before the series capacitor， the phase of the compensation voltage is opposite to the voltage at the relay location; when the fault location is behind the series capacitor， the phase of the compensation voltage is close to the voltage at the relay location. According to the above results， a new method for fault location identification is put forward. Cooperating with traditional distance protection principle， a novel distance protection principle which is adapted to series capacitor compensated line is proposed. When the fault location is before the series capacitor， the distance protection operation is only decided by the characteristics of the impedance relay， immune to the effects of the series capacitor. This new principle can effectively avoid the overreach problem of distance relays and its sensitivity is generally not affected by series compensated capacitors. The validity and reliability of this principle is verified by Electro-Magnetic Transient Program（EMTP）.