engineering recuitment MAHATRANSCO AE Electrical Mock Test Power Systems Protective Relays Directional Relays
For the three-bus power system shown in the figure, the trip signals to the circuit breakers B1 to B9 are provided by overcurrent relays R1 to R9, respectively, some of which have directional properties also. The necessary condition for the system to be protected for short circuit fault at any part of the system between bus 1 and the R-L loads with isolation of minimum portion of the network using minimum number of directional relays is
1
R3 and R4 are directional overcurrent relays blocking faults towards bus 2
2
R3 and R4 are directional overcurrent relays blocking faults towards bus 2 and R7 is directional overcurrent relay blocking faults towards bus 3
3
R3 and R4 are directional overcurrent relays blocking faults towards Line 1 and Line 2, respectively, R7 is directional overcurrent relay blocking faults towards Line 3 and R5 is directional overcurrent relay blocking faults towards bus 2
4
R3 and R4 are directional overcurrent relays blocking faults towards Line 1 and Line 2, respectively.
5
None of these