Exams › GATE › Technical

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.

Correct answer: 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

Solution

The correct option ensures that each relay effectively isolates faults in their respective lines while preventing unnecessary disconnections in other parts of the system. By using directional relays R3, R4, R7, and R5, the system can selectively trip only the affected sections, maintaining stability and minimizing disruption.

Related GATE Technical questions

• If the input x(t) and output y(t) of a system are related as y(t) = max(0, x(t)), then the system is
• Two discrete-time linear time-invariant systems have impulse responses h1[n] = δ[n−1] + δ[n+1] and h2[n] = δ[n−1] + δ[n+1], where δ[n] is the Kronecker delta. The overall system is
• Consider a power system consisting of N number of buses. Buses in this power system are categorized into slack bus, PV buses and PQ buses for load flow study. The number of PQ buses is N_L. The balanced Newton-Raphson method is used to carry out load flow study in polar form. H, S, M, and R are sub-matrices of the Jacobian matrix J as shown below: [ΔP] [ΔQ] = J [Δδ] [ΔV], where J = [H S M R] The dimension of the sub-matrix M is
• Inductance is measured by
• In the Nyquist plot of the open-loop transfer function G(s)H(s) = (3s + 5)/(s - 1) corresponding to the feedback loop shown in the figure, the infinite semi-circular arc of the Nyquist contour in s-plane is mapped into a point at
• Consider a unity-gain negative feedback system consisting of the plant G(s) (given below) and a proportional-integral controller. Let the proportional gain and integral gain be 3 and 1, respectively. For a unit step reference input, the final values of the controller output and the plant output, respectively, are G(s) = 1/(s - 1)

⚔️ Practice GATE Technical free + battle 1v1 →