Optimum Adaptive Relaying Using Fault Current Quadrature (Q) Component

When a microgrid switches from the grid-connected mode to the islanded mode (no utility grid), overcurrent relays must detect any rapid shift in the fault currents. Even, for the low X/R ratio based distributed generators, the fault current variations must also be sensed in time by the relays. Mal-operation and inappropriate coordination may happen due to different available currents before conventional protection (existing relay settings) schemes. To minimize this impact of mis-coordination among relays, optimum current settings with adaptive nature (change as per change in current magnitude) is proposed and verified for earth and phase faults, in the current research work. Only the q (quadrature) component of the fault current is taken into consideration when testing various microgrid operating modes. For backup relays, the suggested quadrature component-based technique also optimizes the fuse coordination-time as a backup to relays.