246. A 66 kV system has string insulator having five discs and the earth to disc capacitance ratio at 0.10. The string efficiency will be ________%

1. 1. 60.7

   
   
   

   2. 6.07

   
   
   

   3. 67

   
   
   

   4. 6.7

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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247. The per unit impedance of a circuit element is 0.15. If the base kV and base MVA are halved, then the new value of the per unit impedance of the circuit element will be ___________

1. 1. 30.3

   
   
   

   2. 0.030

   
   
   

   3. 0.30

   
   
   

   4. 30

   
   
   

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   Xnew =	KVA(new)	×	(KV old)²
   	KVA (old)		(KV new)²

   
   

   =	1/2	×	1	× xold = 2 × 0.15 = 0.30
   	1		(1/2)²

   Correct Option: C

   Xnew =	KVA(new)	×	(KV old)²
   	KVA (old)		(KV new)²

   
   

   =	1/2	×	1	× xold = 2 × 0.15 = 0.30
   	1		(1/2)²

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248. An alternator having induced emf of 1.6 p.u. is connected to an intinite bus of 1.0 p.u. If the bus has reactance of 0.6 p.u. and alter nator has reactance of 0.2 p.u., the maximum power that can be transferred is given by ________ p.u.

1. 1. 2 p.u

   
   
   

   2. 20.2 p.u

   
   
   

   3. 0.02 p.u

   
   
   

   4. 0.2 p.u

   
   
   

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   Pmax =	VƒEƒ	=	1.6 × 1.0	= 2 p.u
   	Xs		100

   Correct Option: A

   Pmax =	VƒEƒ	=	1.6 × 1.0	= 2 p.u
   	Xs		100

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249. A power station consists of two synchronous gener at or s A and B of rating 250 M VA and 500 M VA with inertia 1.6 p.u. and 1 p.u. respectively on their own base MVA ratings. The equivalent P.U inertia for the system on 100 MVA common base will be ____________

1. 1. 9 p.u.

   
   
   

   2. 9.99 p.u.

   
   
   

   3. 9.09 p.u.

   
   
   

   4. 0.09 p.u.

   
   
   

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   H₁ S₁ + H₂ S₂ = HS
   

   Equivalent p.u =	250 × 1.6 + 500 × 1	= 9 p.u.
   	100

   Correct Option: A

   H₁ S₁ + H₂ S₂ = HS
   

   Equivalent p.u =	250 × 1.6 + 500 × 1	= 9 p.u.
   	100

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250. Reflection coefficient for the transmission line shown in the given figure, is __________
     

1. 1. 0

   
   
   

   2. 1

   
   
   

   3. 2

   
   
   

   4. 3

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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