Power system-2

Power system-2 bits

1.     Insulators used on eht transmission lines are made of

2.     Corona is

3.     The sag of the transmission line is least affected owing to

4.     The effect of bonding the cable is

5.     The insulator is so designed that it should fail only

6.     The current drawn by the line owing to corona loss is

7.     100 % string efficiency means

8.     The minimum clearance of high voltage lines from ground across streets is

9.     Dielectric strength of rubber is about

10.                        The diameter of each strand is "d'' then the diameter of n-layer stranded conductor will be

11.                         if the frequency of a transmission system is changed from 50hl to 100hz the string efficiency

12.                         stringing charts can be drawn between

13.                        . The only advantages of corona is that it

14.                        . The conductors are provided by the dampers which

15.                        The use of guard ring

16.                        . With the rise in temperature, the insulation resistively

17.                        Skin effect in a conductor becomes more pronounced

18.                        String efficiency decides

19.                        Proximity of a line to the earth surface

20.                        Oil - filled cables have the draw back (s) of

21.                        The cables used for 132 kv are

22.                        Spacing of conductors should be such so as to provide

23.                        What is skin effect?

24.                        Suspension type insulators are used for voltages beyond

25.                         corona losses are minimized when

26.                        Sulphur hexafluoride cable is insulated by

27.                        The unit nearest to the conductor in suspension type insulator string is under

28.                        String efficiency decides

29.                        The insulators used in guy cables are

30.                        The tension is inversely proportional to the

31.                        The relative permittivity of rubber is b/w

32.                        The sag is inversely proportional to the

33.                        Paper as an insulating material has the main draw back that it

34.                        In capacitance grading of cables, the dielectric used is

35.                        A cable carrying ac has

36.                        The ratio of puncture voltage to the flashover voltage of a line insulator is

37.                        Corona is affected by

38.                        The capacitance of a cable increases

39.                        The charging current drawn by the cable

40.                        The use of guard ring

41.                        Shackle insulators are used on

42.                        The surge impedance of a 50 miles long underground cable is 50ω , for a 25 miles length it will be

43.                        Which of the following protects the under ground cables against mechanical injury?

44.                        Corona is minimum in which type of conductor?

45.                        Reflection co-efficient for open circuited line is?

46.                        Reflection co-efficient for short circuited line is?

47.                        What is acsr?

48.                        What is ferranti effect?

49.                        Which relay is used for short transmission line?

50.                        Which relay is used for medium transmission line?

Power system-2 Keys

1.     porcelain

2.     complete breakdown of air

3.     current through the conductor

4.     to increase the effective resistance but reduce inductance

5.     flash-over

6.     non-sinusoidal

7.     equal potential across each insulator disc

8.     6m

9.     30 kv/mm

10.                        (2n+1)d

11.                        remain unchanged

12.                        temperature - tension and temperature – sag

13.                        works as a safety valve for surges

14.                        prevent the resonant vibrations

15.                        equalizes the voltage distribution between insulator discs

16.                        reduces exponentially

17.                        at higher frequency

18.                        current distribution along the string

19.                        increases the capacitance to natural

20.                        greater cost and complicated laying of cables and maintenance

21.                        extra super voltage

22.                        safety against flashover

23.                        the conductor carries more current on the surface in comparison to its more this phenomenon is called the skin effect

24.                        33 kv

25.                        by using smooth conductor

26.                        compressed gas

27.                        minimum electrical stress

28.                        current distribution along the string

29.                        egg or stay insulators

30.                        temperature

31.                        2 – 3

32.                        working tensile strength of conductor

33.                        is hygroscopic

34.                        composite

35.                        hysterisis and leakage losses only

36.                        much greater than 1

37.                        operating voltage

38.                        linearly with the increase in cable length

39.                        leads the voltage by 90^o

40.                        equalizes the voltage distribution between insulator discs

41.                        low voltage dead end

42.                        52ohms

43.                        armoring

44.                        hollow type of conductor.

45.                        1

46.                        -1

47.                        aluminum conductor steel reinforced

48.                        when ever a transmission line is subjected to load or lightly loaded then the receiving end voltage is greater than the sending end voltage.

49.                         reactance relay

50.                        impedance