156. An extra high voltage transmission line of length 300 km can be approximated by a lossless line having propagation constant β = 0.00127 radians per km. Then percentage ratio of line length to wavelength will be given by

1. 1. 24.24%

   
   
   

   2. 12.12%

   
   
   

   3. 19.05%

   
   
   

   4. 6.06%

   
   
   

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1. View Hint View Answer Discuss in Forum

   Wavelength, λ =	2π	=	2π	= 4947.39 km
   	β		0.00127

   
   

   ∴ Ratio =	Line length	=	300 km	= 0.0606
   	wavelangth		4947.39 km

   
   ∴ % Ratio = 6.06%

   Correct Option: D

   Wavelength, λ =	2π	=	2π	= 4947.39 km
   	β		0.00127

   
   

   ∴ Ratio =	Line length	=	300 km	= 0.0606
   	wavelangth		4947.39 km

   
   ∴ % Ratio = 6.06%

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157. A two machine power system is shown below. Transmission line XY has positive sequence impedance of Z<sub>1 Ω and zero sequence impedance of Z0 Ω.
     
     An ‘a’ phase to ground fault with zero fault impedance occurs at the centre of the transmission line. Bus voltage at X and line current from X to F for the phase ‘a’, are given by Va Volts and Ia Amperes, respectively. Then, the impedance measured by the ground distance relay located at the terminal X of line XY will be given by</sub>

1. 1. Z1	Ω
      2

   
   
   

   2. Z0	Ω
      2

   
   
   

   3. (Z0 + Z1)	Ω
      2

   
   
   

   4. Va	Ω
      Ia

   
   
   

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1. View Hint View Answer Discuss in Forum

   Impedance measured by ground distance relay
   

   =	Bus Voltage	=	Va	Ω
   	Current		Ia

   Correct Option: D

   Impedance measured by ground distance relay
   

   =	Bus Voltage	=	Va	Ω
   	Current		Ia

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158. A 500 M W, 21 k V, 50 H z, 3-phase, 2-pole synchronous generator having a rated p.f.= 0.9 has a moment of inertia of 27.5 × 10³ kg-m². The inertia constant (H) will be

1. 1. 2.44 s

   
   
   

   2. 2.71 s

   
   
   

   3. 4.88 s

   
   
   

   4. 5.42 s

   
   
   

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1. View Hint View Answer Discuss in Forum

   Machine rating (G) =	P	=	500MW	= 555.56 MVA
   	cosφ		0.9

   
   

   Synchronous speed, Ns =	120 × 50	= 3000 rpm
   	2

   
   

   Stored KE =	1	× M ×		2πN		²
   	2			60

   
   

   Stored KE =	1	× 27.5 × 10³		2π × 3000		²
   	2			60

   
   = 1357.07 MJ
   

   Inetria Constant,H =	KE	=	1357.07	= 2.44s
   	MVA		555.56

   Correct Option: A

   Machine rating (G) =	P	=	500MW	= 555.56 MVA
   	cosφ		0.9

   
   

   Synchronous speed, Ns =	120 × 50	= 3000 rpm
   	2

   
   

   Stored KE =	1	× M ×		2πN		²
   	2			60

   
   

   Stored KE =	1	× 27.5 × 10³		2π × 3000		²
   	2			60

   
   = 1357.07 MJ
   

   Inetria Constant,H =	KE	=	1357.07	= 2.44s
   	MVA		555.56

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159. Three generators are feeding a load of 100 MW. The details of the generators are given below.
     

     	Rating	Efficiency	Regulation
     	(MW)	(%)	(p.u) on 100 MVA base
     Generator-1	100	20	0.02
     Generator-2	100	30	0.04
     Generator-3	100	40	0.03

     
     In the event of increased load power demand, which of the following will happen?

1. 1. All the generators will share equal power

   
   
   

   2. Generat or -3 will share more power compared to Generator-1

   
   
   

   3. Generat or -1 will share more power compared to generator-2

   
   
   

   4. Generat or -2 will share more power compared to Generator-3

   
   
   

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1. View Hint View Answer Discuss in Forum

   Generators having better regulation will share more power. So generator 1 will share more power than generator 2.

   Correct Option: C

   Generators having better regulation will share more power. So generator 1 will share more power than generator 2.

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160. Match the items in List-I with the items in List-II and select the correct answer using the codes given below the lists.
     

     List I	List II
     (Type of transmissi on line)	(Type of distance relay preferred)
     A. Short Line	1. Ohm Relay
     B. Medium Line	2. Reactance Relay
     C. Long	3. Mho Relay

     
     Codes:

1. 1. A B C
      2 1 3

   
   
   

   2. A B C
      3 2 1

   
   
   

   3. A B C
      1 2 3

   
   
   

   4. A B C
      1 3 2

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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