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

Distance relays due to their selectivity and operating speed are applied for HV/EHV line protection. The dynamic nature of Mho characteristic, which happens to be most primitive technique in line protection implemented with distance relaying, is built by using the measurement of local voltage and current signals. These signals have been influenced substantially by fault resistance and the source impedance feeding the line. Environmental benefit of wind turbine technology is making it a potential source of energy. These wind turbine generating units (WTGU) use rugged Induction/Synchronous Machines along with power electronics converters as controlling equipment. This gives a new challenge to distance relays, as fault current contribution of these sources depends upon converter operational principle. This paper discusses comparative analysis of behavior of Quadrature Polarized Mho (QPM) relay implemented on line protection in systems having traditional thermal synchronous machine and another system with Doubly Fed Induction Generator (DFIG) based wind farms. The results are illustrated with appropriate graphs and discussed at the end with concluding suggestions.