An Adaptive Relaying Scheme for Fuse Saving

In some situations, utilities may try to ?>save?> the fuse of a circuit following temporary faults by de-energizing the line with the fast operation of an upstream recloser before the fuse is damaged. This fuse saving practice is accomplished through proper time coordination between a recloser and a fuse. However, installation of microgrid distributed generation (DG) into distribution networks may affect this coordination due to additional fault current contribution from the distributed resources. This phenomenon of recloser-fuse miscoordination is investigated in this chapter with the help of a typical network that employs fuse saving. Limitations of a recloser equipped with time and instantaneous overcurrent elements in respect of fuse saving in the presence of DG is discussed. An adaptive relaying strategy is proposed to ensure fuse saving in the new scenario even in the worst fault conditions. The simulation results obtained by adaptively changing relay settings in response to changing DG configuration confirm that the settings selected theoretically in accordance with the proposed strategy hold well in operation¹.