During a power failure, a domestic household uninterruptible power supply (UPS) supplies AC power to a limited number of lights and fans in various rooms. As per a Newton-Raphson load-flow formulation, the UPS would be represented as a

The bus admittance  matrix of a 3-bus power system is given below.

Considering that there is no shunt inductor connected to any of the buses, which of the following can NOT be true?

The three-bus power system shown in the figure has one alternator connected to bus 2 which supplies 200 MW and 40 MVAr power. Bus 3 is infinite bus having a voltage of magnitude  p.u. and angle of . A variable current source,  is connected at bus 1 and controlled such that the magnitude of the bus 1 voltage is maintained at

1.05 p.u. and the phase angle of the source current, , where  is the phase angle of the bus 1 voltage. The three buses can be categorized for load flow analysis as

Bus 1 Slack Bus

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 . 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:

The dimensions of the sub-matrix M is

A 3-Bus network is shown. Consider generators as ideal voltage sources. If rows 1, 2 and 3 of the  matrix correspond to Bus 1, 2 and 3 respectively, then  of the network is

Out of the following options, the most relevant information needed to specify the real power (P) at the PV buses in a load flow analysis is

Two buses, i and j, are connected with a transmission line of admittance Y, at the two ends of which there are ideal transformers with turns ratios as shown. Bus admittance matrix for the system is:

The  matrix of a two-bus power system having two identical parallel lines connected between them in pu is given as          

The magnitude of the series reactance of each line in pu (round off up to one decimal place) is ________________.

A bus admittance matrix for an electric power system has 8000 non-zero elements. The minimum number of branches (transmission lines and transformers) in this system is _____ (up to 2 decimal places).

The figure shows the per-phase representation of a phase-shifting transformer connected between buses 1 and 2, where  is a complex number with non-zero real and imaginary parts.

For the given circuit,  and  are bus admittance matrix and bus impedance matrix, respectively, each of size 2 × 2. Which one of the following statements is true?

A 10-bus power system consists of four generator buses indexed as G1, G2, G3, G4 and six load buses indexed as L1, L2, L3, L4, L5, L6. The generator-bus G1 is considered as slack bus, and the load buses L3 and L4 are voltage controlled buses. The generator at bus G2 cannot supply the required reactive power demand, and hence it is operating at its maximum reactive power limit. The number of non-linear equations required for solving the load flow problem using Newton-Raphson method in polar form is _____________.

A 3-bus power system is shown in the figure below, where the diagonal elements of Y-bus matrix are:

The per unit values of the line reactance’s p, q and shown in the figure are  

The bus admittance matrix for a power system network is

There is a transmission line, connected between buses 1 and 3, which is represented by the circuit shown in figure.  

If this transmission line is removed from service, what is the modified bus admittance matrix?  

In a load flow problem solved by Newton-Raphson method with polar coordinates, the size of the Jacobian is 100 × 100. If there are 20 PV buses in addition to PQ buses and a slack bus, the total number of buses in the system is

In a 100 bus power system, there are 10 generators. In a particular iteration of Newton Raphson load flow technique (in polar coordinates), two of the PV buses are converted to PQ type. In this iteration,

A power system has 100 buses including 10 generator buses. For the load flow analysis using Newton-Raphson method in polar coordinates, the size of the Jacobian is

Determine the correctness or otherwise of the followings Assertion [a] and Reason [r]

Assertion: Fast decoupled load flow method. Gives approximate load flow solution because it uses several assumptions.

Reason: Accuracy depends on the power mismatch vector tolerance.

A 3-bus power system network consists of 3 transmission lines. The bus admittance matrix of the uncompensated system is

If the shunt capacitance of all transmission lines is 50% compensated, the imaginary part of the  row  column element (in pu) of the bus admittance matrix after compensation is

A 183-bus power system has 150 PQ buses and 32 PV buses. In the general case, to obtain the load flow solution using Newton-Raphson method in polar coordinates, the minimum number of simultaneous equations to be solved is

For a power system network with n nodes,  of its bus impedance matrix is j0.5 per unit. The voltage at node 3 is  per unit. If a capacitor having reactance of –j3.5 per unit is now added to the network between node 3 and the reference node, the current drawn by the capacitor per unit is

In the following network, the voltage magnitudes at all buses are equal to 1 p.u., the voltage phase angles are very small, and the line resistances are negligible. All the line reactances are equal to j1 Ω.

The voltage phase angles in rad at buses 2 and 3 are

In the following network, the voltage magnitudes at all buses are equal to 1 p.u., the voltage phase angles are very small, and the line resistances are negligible. All the line reactances are equal to j1 Ω.

If the base impedance and the line-to-line base voltage are 100 Ω and 100kV, respectively, then the real power in MW delivered by the generator connected at the slack bus is

The bus admittance matrix of a three-bus three-line system is

If each transmission line between the two buses is represented by an equivalent -network, the magnitude of the shunt susceptance of the line connecting bus 1 and 2 is

A three-bus network is shown in the figure below indicating the p.u. impedance of each element.  

The Bus admittance matrix, Y-bus, of the network is

For the Y-bus matrix of a 4-bus system given in per unit, the buses having shunt elements are

The figure below shows a three phase self-commutated voltage source converter connected to a power system. The converter's dc bus capacitor is marked as C in the figure. The circuit is initially operating in steady state with δ = 0 and the capacitor dc voltage is equal to . You may neglect all losses and harmonics. What action should be taken to increase the capacitor dc voltage slowly to a new steady slate value?

The Gauss Seidel load flow has following disadvantages.  Tick the incorrect statement.

The network shown in Figure has impedances in p.u. as indicated. The diagonal element of the bus admittance matrix YBUS of the network is:

The Z matrix of a 2-port network as given by

The element of the corresponding Y matrix of the same network is given by

A power system consists of 300 buses out of which 20 buses are generator buses, 25 buses are the ones with reactive power support and 15 buses are the ones with fixed shunt capacitors. All the other buses are load buses. It is proposed to perform a load flow analysis for the system using Newton-Raphson method. The size of the Newton-Raphson Jacobian matrix is

The bus impedance matrix of a 4-bus power system is given by

A branch having an impedance of j0.2Ω is connected between bus 2 and the reference. Then the values of and of the bus impedance matrix of the modified network are respectively.

A power system consists of 2 areas (Area 1 and Area 2) connected by a single tie line (Figure). It is required to carry out a load flow study on this system. While entering the network data, the tie-line data (connectivity and parameters) is inadvertently left out. If the load flow program is run with this incomplete data

For the Y-bus matrix given in per unit values, where the first, second, third and fourth row refers to bus 1, 2, 3 and 4 respectively, draw the reactance diagram.

In a 3-bus system, Gauss load flow method is to be used for finding the switched capacitor compensation required to maintain the voltage at bus 2 equal to 1.0p.u. the data for the system is as follows

Line data :  Neglect line charging.

Bus data :

All data are on common base values.

For the given network in fig., obtain the bus admittance matrix  using the data given:

If the reference bus is changed in two load flow runs with same system data and power obtained for reference bus taken as specified P and Q in the latter run

In load-flow analysis, a voltage-controlled bus is treated as a load bus in subsequent iterations if a reactive power limit is violated. (True=1/False=0)

In load flow analysis, the load connected at a bus is represented as

In load flow studies of a power system, the quantities specified at a voltage-controlled bus are _______________ and _______________

A sample power system network is shown in figure. The reactance’s marked are in p.u. The p.u value of  of the Bus Admittance Matrix  is: