Important question of SGP

                          SWITCH GEAR  AND PROTECTION

                                            UNIT-1

                                              2013-14

1.      What are the essential requirements of protection system?

2.      Differentiate the following :
(a)Primary & back up protection
(b)Pick up & reset value
(c)Operation time & reset time
(d)Normal & abnormal conditions.

3.      Derive the torque equation expression for the induction type relay.

4.      Describe the gas actuated relay.

5.      What are the design considerations in electromagnetic relay.

6.      Describe any vibrationless attracted  armature type relay.
                               2009-10

1.      "Relay is the brain of protection". Justify this statement using trip circuit.

2.      Describe about primary and backup protection. What is meant by time graded over current protection ?

3.      Discuss about any four major qualities a relay should possess.

4.      Draw a neat diagram of gas actuated relay. What is its location and use in the device

5.      Discuss about wattmetric type induction disc relay in detail.

6.      Define the following
Pick-up
Drop out
Reset
Interlock
Blind spot.

2008-09

1.   What are primary and back-up protections?     10

2.  What are various kinds of back-up protections?

3.  Draw a neat sketch of an induction disc or cup type relay and explain its principle of operation.

4.  Discuss the working principle, types and applications of thermal relays.

Unit-2

2013-14

1.      Derive the characteristic equation for phase comparator under threshold condition.

2.      Derive the characteristic of impedance ,reactance & offset Mho relays.

3.      What are the basic elements of  a static relay?. Describe the function of each element.

                                                          2012-13

1.      Enumerate any six major advantages of static relays over electromagnetic  relays & explain them.

2.      Draw  neat diagrams to demonstrate ‘Trip’, restrain & threshold conditions for the sine & cosine types of comparators.

3.      Describe in detail the synthesis of a Mho relay using static phase comparators.

2009-2010

4. Discuss about phase and amplitude comparators in detail.

5. What is a distance relay ? Draw its characteristics. How is directional feature added with over current relays ? Why is it required ?

6. Compare a static relay with electromagnetic relays.

2008-09

1.  Describe various types of phase comparators 10 used in static relays.

2.  Classify various types of over current relays 10 and give their applications alongwith their approximate characteristics and general time-current equations.

unit-3

                                                    2013-14

1.      What is the principle of distance relaying?  Explain definite –distance time graded method of distance protection.

2.      Describe the different component of carrier protection scheme & explain phase comparison carrier protection.

3.      What are the limitations of wire-pilot protection?. Describe the Translay & Solkor schemes.

2012-13

1.      Explain with the help of suitable diagrams the effects of arc resistance & power swings on performance of plane impedance , reactance & Mho relay.

2.      Differentiate between instantaneous DTOC & IDMT relays. Explain with the help of a diagram the time graded OC protection of a doubly fed feeder.

3.      Write a detailed note on pilot wire protection of a transmission line

                                         2009-2010

1.      Describe different types of distance relays used for protection of transmission lines. Which one is the best and why ?

2.      Describe pilot wire protection, its merits and demerits in detail.

3.  How is a bus bar protected ?

                                 2008-09

1.  Draw and explain the characteristics of a MHO relay. Why a MHO relay is preferred for protection of longlives against phase faults ?

2.  Explain with a suitable example the phenomenon of auto reclosing.

3.  Explain the term 'pilot' with reference to power line protection. What are the different types of pilot schemes which are presently employed in transmission line protection?
unit-4

1.      Describe the equipments used in the testing station of CB & draw the layout of testing station.

2012-13

1.      What  do you understand by high arc resistance & low arc resistance method of arc quenching?. Describe two theories related to arc extinction.

2.      Draw the current & voltage waveforms showing  AC CB phenomenon. Show the following in the diagram & describe them.
Major  current loop system voltage Arc voltage restriking voltage, Active recovery voltage, Recovery voltage
What do you understand by Breaking & Making current.

3.      Explain with the help of a suitable diagrams as to what happens when a current is chopped by a CB before its natural zero.

4.      What is the difficulty faced while breaking the fault current of a short transmission line.

5.      Give the detailed description of indirect testing of a CB.

6.      How are the CB classified?. Give details of the same.

2009-2010

1.      What are the problems associated with short line interruption ? How is the problem eliminated ?

2.      Describe about the direct and indirect testing procedure for a circuit breaker.

3.      Discuss about RRRV. Draw a neat diagram to show the voltages and current during relay and circuit breaker operations. Discuss about active recovery voltage, relay operating time, circuit breaking time and circuit making time

                              2008-09

1.  What is the significance of RRRV in operation of a circuit breaker. Also derive the relation for RRRV considering a simple power system.

2.  What are the different tests carried out on a circuit breaker? Differentiate and explain type and routine tests.

3.  What is the difference between direct and indirect testing? Also describe the procedure of indirect testing.
                                      unit-5

2013-14

1.      Discuss the advantages & disadvantages of air blast CB. Describe its method for interrupting the fault current.

2.      Describe the principle of Merze Price system of protection applied to the alternator. What are the shortcomings of this scheme & how are they overcome.

2012-13

1. draw & describe complete protection of an Alternator.

2. Draw & describe the operational details of an SF₆ CB.

3. Discuss in detail about a DC CB with suitable diagram & waveforms.

2009-2010

1.      Describe the construction and operation of a minimum oil circuit breaker.

2.      Draw appropriate diagrams to show the complete operation of a sf₆ circuit breaker. Give the merits of sf₆ circuit breakers.

3.      Give a complete protection scheme for Alternator.

2008-09

1.  Discuss the behaviour of electric arc in vacuum with the help of a neat diagram. Explain the construction of a vacuum circuit breaker.

2.  Explain the construction and working of a puffer type SF₆ circuit breaker. Also enumerate the properties of SF₆ gas which make at a good dielectric and arc quenching medium.

3.  Explain the protection of a three phase star connected generator by means of a percentage differential relay.