v_vista-C 4.0 (kV) 0.0 -4.0 (kA) (kA) (kA) x (kA) -4.0 10.0 5.0 0.0 -5.0 -10.0 (kA) (kV) 0.0 10.0 5.0 0.0 -5.0 -10.0 10.0 5.0 0.0 -5.0 -10.0 10.0 5.0 0.0 -5.0 -10.0 10.0 5.0 0.0 -5.0 -10.0 v_vista-C 4.0 Fault Is Applied 10.0 5.0 0.0 -5.0 -10.0 (kA) Fault Is Applied Fault Is Cleared by C3 i_fault i_gen 2.90 3.00 3.10 3.20 x 3.30 Fault Is Cleared by C1 and C2 i_fault i_relay-C1 i_relay-C2 i_gen 2.90 3.00 3.10 3.20 3.30 (b) (a) Figure 14. The simulation results in case B1. (a) The fault is cleared by the load-way PD. (b) The load-way PD failed to clear the fault, which is cleared by the backup protection provided by loop PDs. v_vista-C 4.0 (kV) (kV) 4.0 0.0 -4.0 v_vista-D (kV) 4.0 0.0 Fault Is Cleared Fault Is by Applied POTT (D2-C1) -4.0 10.0 5.0 0.0 -5.0 -10.0 x (kA) i_relay-C1 10.0 5.0 0.0 -5.0 -10.0 10.0 5.0 0.0 -5.0 -10.0 i_gen 3.00 3.10 3.20 (a) 3.30 10.0 5.0 0.0 -5.0 -10.0 10.0 5.0 0.0 -5.0 -10.0 i_relay-D2 2.90 i_fault Fault Is Isolated by Backup (D2-C2) i_relay-C1 Fault Is Fed Through Vista C i_relay-D2 D2 Tripped; C1 Failed -4.0 (kA) 10.0 5.0 0.0 -5.0 -10.0 i_fault v_vista-D 0.0 (kA) (kA) 10.0 5.0 0.0 -5.0 -10.0 (kA) 10.0 5.0 0.0 -5.0 -10.0 (kA) (kA) Fault Is Applied 0.0 -4.0 (kA) (kV) 4.0 v_vista-C x i_gen 2.90 3.00 3.10 3.20 3.30 (b) Figure 15. The simulation results in case B2. (a) The fault is cleared by the POTT scheme. (b) The fault is isolated by the backup loop PDs once the POTT scheme has failed. 78 I E E E E l e c t r i f i c ati o n M agaz ine / MARCH 2014