C S MAIN 2015 ELECTRICAL ENGINEERING (PAPER-II)

SECTION—A

1. For the block diagram shown in the figure given below, obtain <img src='./qimages/116.1a-i.jpg'> using block diagram reduction technique 10
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A system input (x)-output is described by the relation

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Evaluate the response and its maximum value for an input =2.5 is a unit step function. Given k =25. 10

Name the different types of CROs and mention their applications. Find the velocity of electrons that have been accelerated through a potential of 2000 V in a CRO. 10

Explain the working of an LVDT with a Bourdon tube for the measurement of pressure. 10

Discussing the issues in memory addressing, explain the five addressing modes used in 8085. 10


2. State the Nyquist stability criterion. Draw the complete Nyquist plot and therefrom check the stability of the closed-loop system whose open-loop transfer function i s <img src='./qimages/116.2a.jpg'>

What is pipelining? Explain how it improves the performance of a processor. Discuss how BRANCH like instructions can be handled in a pipelined system.

A machine language program has N instructions, each having m parts.
Suppose each part can be executed in one cycle and there is no BRANCH like instruction in the program. How much time does a processor with pipelining and without pipelining take to execute the program? 10+10=20

Explain the working of a successive-approximation type digital voltmeter using a block diagram. 10

3. The transfer function of a control system is given by

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Derive the state model of the system in controllable phase variable form.
Comment on the observability. What is the value of the smallest time constant of the system? 20

Explain the direct connection method of measurement of Q of a coil. Name the sources of error in such measurements. Compute the value of self-capacitance and inductance of a coil when the following measurements are made 20
At frequency 2 MHz, the tuning capacitor is set at 450 pF
When the frequency is measured to 5 MHz, the tuning capacitor is tuned at 60 pF

What is 8255A PPI? Discuss its blocks—output ports and control logic. Write the instructions to load 65 H in register C and 92 H in accumulator A. Display the number of 65 H and 92 H at PORT 0 and PORT 1 respectively. 5+5=10

4. Briefly discuss the functional classification of the instruction set,
explaining role and format of instructions from each category—data
transfer, arithmetic/logic, branch and control. 10

Discuss the role and purpose of the three buses—address, data and
control. Explain how they connect microprocessor CPU to ROM, RAM
and I/O for data transfer. 5+5=10

What are the sources of errors in an electrodynamometer type wattmeter? A dynamometer type wattmeter connected normally to read power in a 1-phase circuit indicates the value P1. A second reading P2 is obtained when a capacitor of reactance equal to the pressure coil resistance is connected in series with the pressure coil. Show that the phase angle of the load can be obtained from the expression <img src='./qimages/116.4a.jpg'>

The open-loop transfer function of a unity feedback control system is given by

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Determine the value of K so that the gain margin is 20 db. 10

An 11 kV, 50 MVA, 3-phase solidly grounded generator has fault currents at its terminals for different types of faults as follows
ILLL= 1870 A
ILL 2590 A
Ilg 4130 A
Determine p.u. values of sequence reactances of the generator. 10

A transmission line of inductance 0.1 H and resistance of 5 ohms is applied with a voltage v 100sin(wt a represents the instant on voltage wave when short circuit occurs. What should be the instant of short circuit so that DC offset current is zero and maximum? Assume supply frequency as 50 Hz. 10

Explain the advantages of numerical relays. 10

Explain the role of Protocol Data Unit in communication within seven layers of OSI-ISO model. 10

Differentiate between the problems of error detection and correction.
How many check/parity bits are required to correct a single error in a message of m bits? 5+5=10

6. A synchronous generator is feeding 250 MW to a large 50 Hz power system network over a double-circuit line. The maximum steady-state power that can be transmitted over line with both the circuits in operation is 500 MW and is 350 MW with one circuit in operation. A solid 3-phase fault occurring at network end of one of the lines causes it to trip. Estimate critical clearing angle in which circuit breaker must trip so that synchronism is not lost. What further information is needed to estimate critical clearing time? 20

Obtain three zone settings for a reactance relay and a mho relay of 60° from the following data
CT 400/1 A
PT 132 kV/110 V
Impedance for the first section is (2.5 j ohms (primary) and that of second section is (3.5 j7) ohms (primary). The first zone covers 80% of the first section, the second zone covers the first section plus 30% of the second section and the third zone covers the first sectipn plus 120% of the second section. 20

Differentiate between the Pulse Code Modulation and Delta Modulation explaining why DM is considered as a better alternative to PCM. How does the choice of the two parameters—quantization level and sampling interval Ts affect the performance-noise and accuracy/data rate? 5+5=10

7. Determine the equivalent ABCD constants of Network-1 connected in tandem with Network-2 as shown in the figure given below 10

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A transmission line has its electrical length of 5 electrical degrees. Find its physical length. The frequency of supply is 50 Hz. Express the physical length in terms of wavelength of the line. 10

Draw the waveforms showing modulation of the binary signal
0011010010 using ASK, FSK and PSK. 10

What is Quadrature Phase Shift Keying How does it help to
improve the data transmission rate? 10

Draw the block diagram and explain various components involved in digital signal processing for a numerical relay. 10

8. A system consists of two plants (plants 1 and connected by a tie-line and load is located at plant 2. When 100 MW is transmitted from plant a loss of 10 MW takes place on the tie-line. Determine the generation schedule at both the plants and the power received by the load when Y(lamda) for the system is Rs. 25 per MW-hr and fuel inputs to the two plants are given by

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What are the advantages and limitations of air-blast circuit breaker? 10

It is required to install a circuit breaker for a 3-phase, 50 Hz, 220 kV,
500 MVA substation. Select the suitable circuit breaker along its
specifications. 10

Describe the Cyclic Redundancy Check scheme for error detection. Explain how the Frame Check Sequence and divisor/pattern are chosen. Given a message 1010001101 (10 bits), pattern P 110101 bits), illustrate how FCS can be calculated. 5+5=10