66. The incremental cost character istics of two generators delivering 200 MW are as follows:
    

    dF1	= 2.0 + 0.01P1;
    dP1

    
    

    dF2	= 1.6 + 0.2 P2;
    dP2

    
    For economic operation, the generations P₁ and P₂ should be

1. 1. P₁ = P₂ = 100 MW

   
   
   

   2. P₁ = 80 MW, P₂ = 120 MW

   
   
   

   3. P₁ = 200 MW, P₂ = 0 MW

   
   
   

   4. P₁ = 120 MW, P₂ = 80 MW

   
   
   

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1. View Hint View Answer Discuss in Forum

   P₁ + P₁ = 200
   

   and	dF1	=	dF2
   	dP1		dP2

   Correct Option: D

   P₁ + P₁ = 200
   

   and	dF1	=	dF2
   	dP1		dP2

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67. A synchronous generator connected to infinite bus delivers power at a log p.f. If its excitation is increased

1. 1. the terminal voltage increases

   
   
   

   2. voltage angle δ increases

   
   
   

   3. current deliverted increased

   
   
   

   4. both (b) and (c)

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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68. A 100 kVA transformer has 4% impedance and 50 kVA transformer has 3% impedance when they are operated in parallel, which transformer will reach full load first

1. 1. 3%

   
   
   

   2. 4%

   
   
   

   3. data is insufficient

   
   
   

   4. none of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Z1 < Z2	S2(rated)	< 0.03 ×	50
   	S1(rated)		100

   
   

   Z1 < Z2	S1(rated)
   	S2(rated)

   
   

   0.03 < 0.04 ×	100	< 0.08
   	50

   Correct Option: A

   Z1 < Z2	S2(rated)	< 0.03 ×	50
   	S1(rated)		100

   
   

   Z1 < Z2	S1(rated)
   	S2(rated)

   
   

   0.03 < 0.04 ×	100	< 0.08
   	50

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69. A shunt reactor at 100 MVAr is operated at 98% of its rated voltage and at 96% of its rated frequency. The reactive power absorbed by the reactor is

1. 1. 98 MVAr

   
   
   

   2. 104.02 MVAr

   
   
   

   3. 96.04 MVAr

   
   
   

   4. 100.04 MVAr

   
   
   

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1. View Hint View Answer Discuss in Forum

   Reactive Power =	V²	=	V²
   	Xs		2πƒL

   
   

   Preact =	0.98V × 0.98V	/	V²
   	2πL × 0.96ƒ		2πƒL

   
   

   =	0.98 × 0.98	× 100
   	0.96

   
   = 100.04 MVAr

   Correct Option: D

   Reactive Power =	V²	=	V²
   	Xs		2πƒL

   
   

   Preact =	0.98V × 0.98V	/	V²
   	2πL × 0.96ƒ		2πƒL

   
   

   =	0.98 × 0.98	× 100
   	0.96

   
   = 100.04 MVAr

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70. With the help of a reactive compensator it is possible to have

1. 1. constant voltage operation only

   
   
   

   2. unity p.f. operation only

   
   
   

   3. both constant voltage and unity p.f.

   
   
   

   4. either constant voltage or unity p.f.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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