A semiconductor switch needs to block voltage V of only one polarity (V > 0) during OFF state as shown in figure (i) and carry current in both directions during ON state as shown in figure (ii). Which of the following switch combination(s) will realize the same?

The circuit shown in the figure has reached steady state with thyristor 'T' in OFF condition. Assume that the latching and holding currents of the thyristor are zero. The thyristor is turned ON at $$t=0$$ sec. The duration in microseconds for which the thyristor would conduct, before it turns off, is _________ (Round off to 2 decimal places).

The single phase rectifier consisting of three thyristors $$T_1,T_2,T_3$$ and a diode $$D_1$$ feed power to a 10 A constant current load. $$T_1$$ and $$T_3$$ are fired at $$\alpha=60^\circ$$ and $$T_2$$ is fired at $$\alpha=240^\circ$$. The reference for $$\alpha$$ is the positive zero crossing of $$V_{in}$$. The average voltage $$V_0$$ across the load in volts is __________ (Round off to 2 decimal places).

For the three-bus power system shown in the figure, the trip signals to the circuit breakers B$$_1$$ to B$$_9$$ are provided by overcurrent relays R$$_1$$ to R$$_9$$, 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