# While using air-blast circuit breaker current, chopping is a phenomenon

1.  Long overhead line is switched off

2.  Bank of capacitors is switched off

3.  Transformer on no load is switched off

4.  Heavy load is switched off

4
Correct Answer :

Transformer on no load is switched off

Explanation :
No Explanation available for this question

# Lightning arresters are used in power systems to protect electrical equipments against

1.  Direct strokes of lighting

2.  Power frequency of over voltages

3.  Overvoltages due to indirect lightning stroke

4.  Overcurrents due to lightning stroke

4
Correct Answer :

Overvoltages due to indirect lightning stroke

Explanation :
No Explanation available for this question

# To prevent maloperation of differentially connected relay while energizing a transformer, the relay restraining coil is biased with

1.  Second harmonic current

2.  Third harmonic current

3.  Fifth harmonic current

4.  Seventh harmonic current

4
Correct Answer :

Fifth harmonic current

Explanation :
No Explanation available for this question

# Rated breaking capacity (MVA) of a circuit breaker is equal to

1.  Produced of rated breaking current (kA) and rated voltage (kV)

2.  Product of rated symmetrical breaking current (kA) and rated voltage (kV)

3.  Product of breaking current (kA) and fault voltage (kV)

4.  Twice the value of rated current (kA) and rated voltage (kV)

4
Correct Answer :

Produced of rated breaking current (kA) and rated voltage (kV)

Explanation :
No Explanation available for this question

# The transient stability of the power system can be effectively improve by

1.  Excitation control

2.  Phase shifting transformer

3.  Single pole switching of circuit breakers

4.  Increasing the turbine valve opening

4
Correct Answer :

Excitation control

Explanation :
No Explanation available for this question

# During a disturbance on a synchronous machine, the rotor swings from  A to B before finally settling down to a steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at points

1.  A and B

2.  A and C

3.  B and C

4.  only at C

4
Correct Answer :

A and B

Explanation :
No Explanation available for this question

# Steady state stability of a power system is the ability of the power system to

1.  Maintain voltage at the rated voltage level

2.  Maintain frequency exactly at 50 Hz

3.  Maintain a spinning reserve margin at all times

4.  Maintain synchronous between machines and on external tie lines

4
Correct Answer :

Maintain a spinning reserve margin at all times

Explanation :
No Explanation available for this question

# The inertia constant H of a synchronous condenser is

1.  Greater than that of hydro generator

2.  Greater than that of turbo alternator

3.  Equal to that of the effective length of the line

4.  None of these

4
Correct Answer :

None of these

Explanation :
No Explanation available for this question

# A power station consists of two synchronous generators A and B or ratings 250 MVA and 500 MVA with inertia 1.6 p.u and 1 p.u respectively on their own base MVA ratings. The equivalent p.u inertia constant for the system on 100 MVA common base is

1.  2.6

2.  0.615

3.  1.625

4.  9.0

4
Correct Answer :

0.615

Explanation :
No Explanation available for this question

# A power system has two synchronous generators. The governor turbine characteristics corresponding to the generaotors are P1=50(50-f),  P2=100(51-f) where f denotes the system frequency in Hz and P1 and P2 are respectively, the power outputs (in MW) of turbines 1 and 2. Assuming the generators and transmission network to be lossless, the system frequency for a total load of 400 MW is

1.  47.5 Hz

2.  48.0 Hz

3.  48.5 Hz

4.   49.0 Hz

4
Correct Answer :

48.0 Hz

Explanation :
No Explanation available for this question

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