Circuit Breaker Closed L Load WT B Circuit Breaker Open PV Photovoltaic Wind Turbine Utility Grid Batteries Energy Storage PEs Feeder Relay Protection Zone 1 Feeder Relay Protection Zone 2 Bus 5 Bus 6 ICB4 CB5 CB4 IPV Fault CB9 CB10 CB7 CB11 CB6 CB8 Fault Current L L PV CB2 CB1 CB12 Diesel Generator Bus 3 Bus 4 CB13 CB15 CB17 CB18 Bus 1 CB14 CB16 L Bus 2 CB19 L WT CB3 Off-Grid Microgrid B (a) Bus 6 1.2 1 0.6 Line 2 PV Bus 5 ,R fI nc re Zone 1 0.4 as e, Po we rF Line 1 0.2 0 PV Off, Rf Increase On e, as 8 re 0. nc = fI r R cto n, a O er F PV ow P e, as re 0.7 nc fI r= , R cto On r Fa PV we Po X (Ω) 0.8 PV On, Rf Increase, Power Factor = 1 Zone 2 Bus 2 0 2 4 6 8 ac to r= 0. 9 10 R (Ω) (b) figure 6. (a) The distance relay (R3) protection zones and (b) the calculated impedance for different fault resistance values and DER power factors during fault. Rf: fault resistance. 28 ieee power & energy magazine may/june 2021