Abstract: Since the failure characteristics of series compensated lines are more complicated, the distance protection is usually difficult to operate correctly. This paper investigated a new fault location algorithm based on one-terminal signals. This method is conducted by the R-L model of the transmission lines. According to the different fault parameters of the transmission line in front of or behind the series compensation device, two calculation models for distance measurement were presented. By comparing the calculated resistance values with the real values, the relative position of the fault can be located. If a fault takes place in front of the series capacitor, the circuit breaker would be tripped directly. But if the fault takes place behind the series capacitor, the fault location can be found by the presented model and the calculation algorithm mentioned above. This scheme can solve the transient overreach problem in traditional series compensated protection scheme. At the same time, this scheme uses the transient data only before the mental oxide varistor(MOV) conducting, the protection can avoid MOV’s nonlinearity which makes the voltage of series compensated capacitors not easy to obtain. By this method, the reliability of the distance protection can also be improved greatly. At the end, the validity and adaptability of the scheme were verified through the PSCAD simulation.

Key words: series compensated line, distance protection, fault location, R-L model, one-terminal signal