Model recognition longitudinal protection based on modules for transmission lines

By the fault analysis of transmission line,the capacitance model for external fault and the inductance model for internal fault are established.Based on the parameter recognition method using short data-window on time domain,the error between actual transmission line model and capacitance or inductance model is calculated.If the error of inductance model is larger than that of capacitance model,it is the internal fault;otherwise,it is the external fault.In practice,modules are used in the model recognition to reduce the interphase electromagnetic coupling disturbance.By computing the model error,the true state of transmission lines is obtained.Theoretical analysis shows that,the proposed method based on fault components is immune to load state and transition resistance,the capacitance current compensation and the phasor extraction are unnecessary,with less influence of transient components.EMTP simulation demonstrates its fast operation speed and good performance.