# Questions & Answers of Gauss-Seidel and Newton-Raphson Load Flow Methods

## Weightage of Gauss-Seidel and Newton-Raphson Load Flow Methods

Total 13 Questions have been asked from Gauss-Seidel and Newton-Raphson Load Flow Methods topic of Power Systems subject in previous GATE papers. Average marks 1.38.

A 1000 × 1000 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 are _____ (up to 2 decimal places).

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A 10-bus power system consists of four generator buses indexed as G1, G2, G3, G4 and six load buses indexed as L2, L2, L3, L4, L5, L6. The generator-bus G1 is connected 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 popular form is________.

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In a load flow problem solved by newton-Raphson method with polar coordinates, the size of the Jactobian 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__________.

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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,

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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

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Determine the correctness or otherwise of the following Assertion [a] and the 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.

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A two bus power system shown in the figure supplies load of 1.0+j0.5 p.u.

The values of V1 in p.u. and δ2 respectively are

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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 ___________.

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

$Y=j\left[\begin{array}{ccc}-13& 10& 5\\ 10& -18& 10\\ 5& 10& -13\end{array}\right]$

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

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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

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Consider two buses connected by an impedance of (0+j5) Ω. The bus 1 voltage is $100\angle 30°$V, and bus 2 voltage is 100∠ 0o$100\angle 0°$V.The real and reactive power supplied by bus 1, respectively, are

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

${\mathbf{Y}}_{\mathbf{BUS}}\mathbf{=}j\left[\begin{array}{cccc}-5& 2& 2.5& 0\\ 2& -10& 2.5& 4\\ 2.5& 2.5& -9& 4\\ 0& 4& 4& -8\end{array}\right]$

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Consider the two power systems shown in figure A below, which are initially not interconnected, and are operating in steady state at the same frequency. Separate load flow solutions are computed individually of the two systems, corresponding to this scenario. The bus voltage phasors so obtain are indicated on figure A.

These two isolated systems are now interconnected by a short transmission line as shown in figure B, and it is found that P1=P2=Q1=Q2=0.

The bus voltage phase angular difference between generator bus X and generator bus Y after interconnection is