Behavior of self polarized Mho characteristic on lines fed from DFIG based wind farms

Distance relays due to their selectivity and operating speed are applied primarily for HV/EHV line protection. Mho characteristic is most primitive distance relaying technique applied in line protection. The dynamic nature of this characteristic is built by measurement of local voltage and current signals. These signals have substantial influence of fault resistance and the source feeding the line. Environmental benefits of wind turbine technology are making it a potential source of energy of future. These wind turbine generating units (WTGU) use rugged Induction/Synchronous Machines along with power electronics converters. This gives a new challenge to distance relays, as fault current contribution of these sources depends upon converter design. This paper deals with behavior of Self Polarized Mho (SPM) relay implied on line protection experienced in systems having substantial wind energy penetration. Two systems one with traditional thermal synchronous machine and another system with Doubly fed induction generator (DFIG) based wind farm of same capacity have been studied to investigate intended effect.