Important Two Marks & 16 Marks Question and Answers

TWO MARKS QUESTION AND ANSWER

1. What are the components of power system?

The various components of power system includes

i. Generators,

ii. Power Transformers,

iii. Transmission lines,

iv. Substation Transformers,

v. Distribution Transformers and

vi. Loads.

2. What are the main divisions of power system?

If a sudden change or sequence of changes occurs in one or more of the system parameters or one or more of its operating quantities, the system is said to have undergone a disturbance from its steady state operating condition.

The two types of disturbances in a power system are,

i. Large disturbance

ii. Small disturbance

3. What is Power system?

A Power system consists of Generation, Transmission and Distribution, are connected through transmission line, which also connect to power grid to another.

4. What are the components of power system?

The components of power system are Generators, Power transformers,

Transmission lines, Distribution lines, Loads and compensating devices like shunt, series, and static VAR compensator.

5. What is modern power system?

A modern power system can be subdivided into four major parts: Generation,

Transmission and Sub transmission, Distribution and Loads.

6. What are the functions of protective relays. (Nov/Dec-2006, May/June-2007) (or)

Why Protection schemes are needed in power system. (Apr/May 2018)

To detect the fault and initiate the operation of the circuit breaker to isolate the defective element from the rest of the system, thereby protecting the system from damages consequent to the fault.

7. What are unit system and non unit system?

A unit protective system is one in which only faults occurring within its protected zone are isolated. Faults occurring elsewhere in the system have no influence on the operation of a unit system. A non unit system is a protective system which is activated even when the faults are external to its protected zone.

8. What is primary protection? (Nov/Dec 2017)

Is the protection in which the fault occurring in a line will be cleared by its own relay and circuit breaker. It serves as the first line of defence.

9. What is back up protection?

Is the second line of defence, which operates if the primary protection fails to activate within a definite time delay.

10. What is biased differential bus zone reduction?

The biased beam relay is designed to respond to the differential current in terms of its fractional relation to the current flowing through the protected zone. It is essentially an over-current balanced beam relay type with an additional restraining coil. The restraining coil produces a bias force in the opposite direction to the operating force.

11. What are the major protective elements needed for power system and why?

It includes circuit breaker and protective relays because they isolate faulty sections of the system from healthy sections.

12. List the common protective schemes which are used for modern power system and protection?

a. Over current protection

b. Distance protection

c. Distance protection

d. Carrier current protection

e. Differential protection

13. What is the necessity of earthing? And different types. (MAY/JUNE-2015)

The necessity for earthing is to ensure that the metalwork of electrical equipment, other than current carrying parts, cannot have a potential above earth in the event of a fault which might otherwise cause danger of an electric shock. If a fault is developed, causing unearthed metalwork of a piece of electrical equipment; it is charged to a level of dangerous potential. Any person touching the metal & at the same time comes in contact with earth will receive a severe electric shock. Had the metal been effectively earthed, the very low resistance of the circuit would result in a flow of bat current sufficient to blow the Fuse or to operate the protective device. In an earth metalwork of a piece of electrical equipment becomes a zero potential due to this; a bate person does not get a shock.

14. What is circuit breaker?

It is a piece of equipment used to break a circuit automatically under fault Conditions. It breaks a circuit either manually or by remote control under normal Conditions and under fault conditions.

15. Write the classification of circuit breakers based on the medium used for arc extinction? (Nov/Dec-12)

i. Air break circuit breaker

ii. Oil circuit breaker

iii. Minimum oil circuit

iv. Air blast circuit breaker

v. SF6 circuit breaker

vi. Vacuum circuit breaker

16. What is the main problem of the circuit breaker?

When the contacts of the breaker are separated, an arc is struck between them. This arc delays the current interruption process and also generates enormous heat which may cause damage to the system or to the breaker itself. This is the main problem.

17. What are demerits of MOCB?

i. Short contact life

ii. Frequent maintenance

iii. Possibility of explosion

iv. Larger arcing time for small currents

v. Prone to restrict

18. What are the advantages of MOCB over a bulk oil circuit breaker?

i. It requires lesser quantity of oil

ii. It requires smaller space

iii. There is a reduced risk of fire

iv. Maintenance problem are reduced

19. What are the disadvantages of MOCB over a bulk oil circuit breaker?

i. The degree of carbonization is increased due to smaller quantity of oil

ii. There is difficulty of removing the gases from the contact space in time

iii. The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization.

20. Give the difference between Fuse, isolator and CB. (May/June 13, Nov/Dec-12, May-14)

Fuse: Is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit?

Isolator: Which used to make the circuit are close the circuit without load

Circuit breaker: Circuit breaker is the device used to make the circuit are close the circuit either manually or automatically under up normal conditions.

21. Why transmission systems are mostly overhead systems?

Because of the cost consideration, the transmission systems are mostly overhead systems.

22. Mention the transmission voltages that are used in India.

33/66/110/132/220/400/765 kV

23. Mention the material universally employed for overhead transmission line.

ACSR (Aluminium conductor steel Reinforced)

24. What is the Usable Voltage for secondary distribution?

415V and 240V

(415V for 3 phase loads and 240V for 1 phase loads)

25. How transmission lines are classified based on their length?

Short line - Less than 60 km

Medium line - 60 km to 150 km

Long line - More than 150 km

 

PART-B QUESTIONS

1. Explain basic Principle and need for Protective systems.

2. Explain the importance of protective scheme employed in power system.

(April/May-2014) (May 2017)

3. Write notes on various principles of power system protection.

4. Write notes on power system earthing.

5. Explain Power system earthing. What are neutral earthing and its objectives?

6. Discuss and compare the various methods of neutral earthing. (Nov/Dec 2017)

7. Explain different types of earthing the neutral point of the power system. (Dec-15, May-16)

8. Explain in detail about the need and different types of earthing schemes? (Nov/Dec 2016) (Apr/May 2018) (Nov 2018)

9. Describe the operating principle of MCB with Neat sketch.

10. Describe the construction and operating principle of MCCB with Neat sketch.

11. Describe the construction and operating principle of ELCB with Neat sketch.

12. Explain basic structure of power systems and its components.

13. Explain basic concept of Switch fuse units with neat sketch.

14. Explain in detail about safety precaution and first aid.