NEW
Font size
WorksheetsEE8501 POWER SYSTEM ANALYSIS MODEL EXAM NOV 2020
Total questions: 45
Worksheet time: 27mins
1.1 What is the per unit system (PU)?
a) A ratio of actual value in any units to the base or reference value in the same units
b) A ratio of the base or reference value in any units to the actual value in the same units.
c) Ratio of the square of the actual value in any units to the square of base or the reference value in the same units
d) All of these
1.2 Which among these is the major advantage of per unit computations?
a. Per unit impedance of transformers is the same referred to either side of it.
b. For simulating steady state and transient models in the computer this method is very useful.
c. Manufactures usually specify the impedance of an apparatus in per unit system.
d.all of these
1.3 Single line diagram does not represents:
a) Star connection of transformer winding
b) Delta connection of transformer winding
c) Neutral wire of transmission lines
d) Ratings of machines
1.4 What is the main purpose of reactance diagram?
a) Load flow analysis
b) Fault analysis
c) Calculation of ratings of Alternators
d) Calculation of ratings of Transformers
1.5 For n bus power system size of Y bus matrix is
a) (n-1) × (n-1)
b) (n-2)×(n-2)
c) n×n
d) (n-1)× (n-2)
1.6 What is the formula to calculate the (kV)B on the HT section?
a. (kV)B on HT section * (HT voltage rating) / (LT voltage rating)
b. (kV)B on LT section * (HT voltage rating) / (LT voltage rating)
c. (kV)B on HT section * (LT voltage rating) / (HT voltage rating)
d. (kV)B on LT section * (LT voltage rating) / (HT voltage rating)
1.7 (2 marks) What will be the per unit impedance of a synchronous motor having a rating of 100 kVA, 13.2 kV and having a reactance of 75 Ω / ph?
a. 0.043 pu
b. 0.057 pu
c. 0.036 pu
d. 0.298 pu
1.8 (2 marks ) If sparsity of a 5 bus transmission line is 0.4. Find the number of transmission lines?
a) 4
b) 5
c) 6
d) 3
1.9 ( 2 marks) The per unit value of a 2 ohm resistor at 100 MVA and 10 kV base voltage is
a. 4
b. 6
c. 2
d. 2.3
2.1 Why are load flow studies carried out?
a. To study of stability of the system
b. For fault calculations
c. For planning the power system
d. All of these
2.2 Which among the following quantities are specified at the generator bus?
a. P and Q
b. P and |V|
c. Q and |V|
d. P and δ
2.3 What percentage of buses in the power system are generator buses?
a. 5 %
b. 25 %
c. 70 %
d. 10 %
2.4 Which among the following is the main assumption to solve a load flow problem by GS method?[NPTEL]
a. All the buses are to be considered as PQ bus including the slack bus.
b. All the buses are to be considered as PV bus including the slack bus.
c. All the buses are to be considered as PQ bus excluding the slack bus.
d. All the buses are to be considered as PV bus excluding the slack bus.
2.5 In load flow studies PV bus is treated as PQ bus when
a. Phase angle become high
b.Voltage at the bus become high
c. Reactive power goes beyond limit
d. Any of the above
1.6 For accurate load flow calculations on large power systems, the best method is
a. N-R method
b.G-S method
c. Decoupled method
d. All of the above
2.7 (2 marks) Initially what will be the voltage at all the PQ buses for solving the load flow problem using NR method?
a. Vi = 1 ∠ 90°
b. Vi = 1 ∠ 0°
c. Vi = 1 ∠ 180°
d. Vi = 1 ∠ 45°
2.8 ( 2 marks ) In load flow analysis, the load connected at a bus is represented as[GATE]
a. Constant current drawn from the Bus
b. Constant impedance connected at the bus
c. Voltage and frequency dependent source at the bus
d. Constant real and reactive power drawn from the bus.
2.9 (2 marks) Range of accelerating factor is
a.50 to 100
b. 1 to 10
c.1.6 to 1.8
d.10.8 to 11.2
3.1 Which among these is the most severe fault?
a. Single line to ground fault.
b. Double line to ground fault
c. Line to line fault
d. Symmetrical fault.
3.2 In which portion of the transmission system is the occurrence of the fault more common?
a. Alternators
b. Transformers
c. Transmission lines
d. Underground cables
3.3 Which among the following reactance have a greater value?
a. Sub transient reactance
b. Transient reactance
c. Synchronous reactance
d. All of these
3.4 What is the rated breaking capacity of the circuit breaker?
a. The product of rated voltage and rated breaking current
b. The product of rated voltage and rated symmetrical breaking current
c. The product of fault voltage and breaking current
d. None of these
3.5 A balanced three phase system consists of _________.
a. Zero sequence currents only
b. Positive sequence currents only
c. Positive, negative and zero sequence currents
d. Only negative sequence currents
3.6 In a synchronous generator for how much time sub transient period of symmetrical short circuit current lasts?
a) For 200 Cycles
b) For 500 Cycles
c) For 30 Cycles
d) For 2 Cycles
3.7 (2 marks) In the manufacture of transformers, ANSI prescribes certain standards. What is this standard?
a. High voltage side should lead the low voltage side by 30° with Y - Δ or Y - Δ connections.
b. High voltage side should lead the low voltage side by 60° with Y - Δ or Y - Δ connections.
c. High voltage side should lag the low voltage side by 30° with Y - Δ or Y - Δ connections.
d. High voltage side should lag the low voltage side by 60° with Y - Δ or Y - Δ connections
3.8 (2 marks ) What is the expression for the symmetrical short circuit current? If the total short circuit current consists of two parts namely symmetrical short circuit current and DC offset current.
a. (Vm / Z) * sin (ω + αt - θ)
b. (Vm / Z) * sin (ωt + α - θ)
c. (Vm * Z) * sin (ωt + αt - θ)
d. (V / Zm) * sin (ωt + α - θ)
3.9 (2 marks ) Why are series reactors used?
a. Improve the transmission efficiency
b. Improve the power factor of the power system
c. To bring down the fault level with in the capacity of the switch gear instrument
d. All of these
4.1 What are the types of unsymmetrical faults?
a. Single line to ground fault
b. Double line to ground fault
c. Line to line fault
d. All of these
4.2 What is the value of the letter ‘a’ or ‘α’ which is commonly used in symmetrical components?
a. 1 ∠ 90°
b. 1 ∠ 30°
c. 1 ∠ 120°
d. 1 ∠ -120°
4.3 What percentage of faults occurring is single line to ground fault?
a. 50 %
b. 60 %
c. 35 %
d. 70 %
4.4 What are the terminal conditions in case of SLG fault, if the fault occurs in the phase A?
a. Vb = 0, Ia = 0, Ic = 0
b. Va = 0, Ib = 0, Ic = 0
c. Va = 0, Ia = 0, Ic = 0
d. Vb = 0, Ia = 0, Ib = 0
4.5 What is the expression for fault current in line to line fault?
a. If = √3 * (Ea / Z1 + Z2)
b. If = 3 * (Ea / Z1 + Z2)
c. If = √3 * (Ea / Z1 + Z2 + Z0)
d. If = 3 * (Ea / Z1 + Z2 + Z0)
4.6 How are the zero sequence and negative sequence networks connected in case of LLG faults?
a. Parallel
b. Series
c. Can be connected in either way
d. Such type of connection does not exist
4.7 ( 2 marks) The zero sequence depiction of the unbalancing occurring at the terminals of the induction motor will be most likely [GATE]
4.8 (2 marks) Which among these is the connection diagram for line to line faults?
a. Only a
b. Only b
c. Only c
d. Only d
4.9 (2 marks ) Phase shift of symmetrical components happens in which among the following?
a. Delta - delta
b. Star – delta
c. Delta – star
d. Both (b) and (c)
5.1 What is steady state stability limit?
a. The maximum flow of power
through a particular point in the power system without loss of stability small disturbances occur.
b. The maximum power flow possible
through a particular component connected in the power system.
.
c. The maximum flow of power through a particular point in the power system without loss of stability when sudden disturbances occur
d. All of these
5.2 Transient disturbances are caused by
a. Sudden load changes
b. Switching operations
c. Fault in the power system
d. All of the above
5.3 Equal area criterion is applicable to:
a. Single machine connected to infinite bus
b. Two machines connected to infinite bus
c.Multi machine system connected to infinite bus
d. All of these
5.4 The quantity H in swing equation is:
a.Kelvin constant
b.Motion of synchronous motor/3.55
c.Inertia constant
d.None of these
5.5 With the use of high speed circuit breakers, which among the following stability is increased?
a. Steady state stability
b. Transient stability
c. Frequency stability
d. All of these
5.6 What is / are the major assumptions made in the calculation of swing equations?
a. Damper winding are neglected
b. The machine is lossless
c. The machine has to run at synchronous speed
d. Both (a) and (b)
5.7 (2 marks) Which point on the graph represents the steady state stability limit of the system?
a. Point A
b. Point B
c. Point C
d. Point D
5.8 ( 2 marks) Swing equation which describes the relative motion of the rotor of the machine, is a
a) linear and second-order differential equation
b) non linear and second-order differential equation
c) non linear and first-order differential equation
d) non linear and hyperbolic equation
5.9 (2 marks) A variation in the power transfer had been observed at the generating station while power exchange process due to ______ and is known as ______
a) Swing of the machine, inertial response
b) sub synchronism, hunting
c) sub synchronism, inertial response
d) swing of the machine, falling out of the rotor
