Power System BEU Previous year question solution 2021

Bihar Engineering university(beu) previous year question solution. Power system BEU pyq solution 2021. BEU power system notes, organizer . BEU question paper solution. biharengineeringuniversity

1. A generator transformer unit is connected to a line through a circuit breaker. The unit ratings are: Generator: 15 MVA, 11 kV, X = 0.3 p.u., X=0.3 p.u., . 6 p.u. Transformer: 15 MVA, 12-7/66 kV, reactance 0-06 p.u. The system is operating at no load at a line voltage of 66 kV, when a three-phase fault occurs on the line just beyond the circuit breaker. Find- (a) the initial symmetrical r.m.s. current in the breaker (b) the maximum possible d.c. offset current in the breaker; (c) the momentary current rating of the breaker; (d) the current to be interrupted by the breaker and the interrupting kVA; (e) the sustained short-circuit current in the breaker.


2. A single-phase 50 Hz generator supplies an inductive load of 8 MW at a power factor of 0.707 lagging by means of an overhead transmission line 15 km long. The line resistance and inductances are of 0.023 ohm and 0.56 mH per km. The voltage at the receiving end is required to be kept constant at 11 kV. (a) Find the sending end voltage and voltage regulation of the line. (b) Find the value of the capacitors to be placed in parallel with the load such that the regulation is reduced to 60% of that obtained in part (a). (c) Compare the transmission efficiency in parts (a) and (b).


3. Discuss in detail about the over-current and directional protection scheme. Also, discuss in detail about the advantages and disadvantages of both the protection schemes and mention their applications.

4. Discuss in detail about the permanent magnet synchronous generator and induction generator for power generation through wind energy. Also discuss why there is a requirement of using two types of generators. What is the advantage of using one over the other generator?

5. (a) Draw the sequence diagrams of all types of connections of a transformer.

(b) A synchronous machine 1 generating 1 p.u. voltage is connected through a Y/Y transformer of reactance of 0.1 p.u. to two transmission lines in parallel. The other ends of the lines are connected through a Y/Y transformer of reactance of 0.15 p.u. to a machine 2 generating 1 p.u. voltage. For both transformers X₁ = X2 = Xo .Calculate the current fed into a double line to ground fault on the line side terminals of the transformer fed from machine 2. The star points of machine 1 and of two transformers are solidly grounded. The reactance (p.u.) of the machines and lines referred to a common base are as follows: Machine 1: X₁ = 0.45, X2 = 0.35, X = 0.05 Machine 2: X₁ = 0·40, X2 = 0.30, X。 = 0·04 Line each X₁ = 0.30, X2 = 0.30, Xo = 0.64

6. Explain in detail about the sinusoidal steady- state representation of short, medium and transmission lines.

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7. (A) Describe the construction, principle of operation and application of (i) rod gap and (ii) expulsion gap. (b) Explain clearly how the rating of lightning arrester is selected. What is the best location of lightning arrester and why?

8. Explain about the typical waveform of synchronous generator under balanced terminal short-circuit conditions for steady- state, transient and sub-transient equivalent circuit. Derive the essential expressions also.

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