GATE 2019 EE – Question 31

Power Systems · Per-unit quantities, Bus admittance matrix, Gauss-Seidel and Newton-Raphson load flow methods · 1 mark · Numerical answer

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

$$Y_{bus}=\begin{bmatrix}-j8&j20\\j20&-j8\end{bmatrix}.$$

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

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Show answer and explanation

Correct answer: 0.09 to 0.11

Explanation

The off-diagonal element is the negative of the total series admittance between the buses, so the two lines together have admittance magnitude $20$ pu. Each line has $10$ pu, so its series reactance is $\frac{1}{10}=0.1$ pu.