Line protection in inverter supplied networks

New protection methods are required to protect a distribution system when supplied by current limited converters. In this paper, a method of converter control is proposed to limit the current by reducing the voltage in the faulted phase or phases while keeping the voltage of the healthy phases unaltered. Unsymmetrical fault analysis is performed to calculate the sequence currents and voltages at the relay location, when system is supplied by a converter. Based on that converter control, distance relay performances have been evaluated in both grid-connected and islanded mode operations. Distance relay, combined with MHO and negative sequence impedance directional characteristics, is proposed as a protection scheme for the distribution system for different types of faults under the current limited environment. The results are validated through PSCAD/EMTDC simulation and MATLAB calculations.