WorksheetsPSA UNIT 4-I
Total questions: 55
Worksheet time: 29mins
How will you calculate the Per unit value?
Base value/Actual value
Actual value/Per unit value
Per unit value/Actual value
Actual value/Base value
List of parts of Power system.
Generation, transmission and distribution.
generation, transmission and transformer
generation, impedance and distribution.
Motor, transmission and distribution.
What are the different methods available to construct bus admittance matrix?
Direct Inspection method
Singular Transformation methods
Both Direct Inspection method and Singular Transformation methods
None of the above
Which is "NOT" an objective of the Power System Analysis??
To design the circuit breakers
To plan future expansion of the existing power system
To analyze the system under different fault conditions and also to analyze the stability of the system
To reduce the reliability of the power system
Choose the base MVA for the given power system:
G1: 100 MVA; 33 kV; X=10%
G2: 150 MVA; 33 kV; X=20%
G3: 200 MVA; 33 kV; X=15%
100 MVA
150 MVA
200 MVA
122.5 MVA
Which one has the correct order of steps to find bus admittance matrix using singular transformation method?
1.Multiplication of[AT][Y][A]
2.Bus incidence Matrix
3.Transpose of Bus incidence Matrix
4.Oriented Graph
5.Calculation of Yprimitive
1.Bus incidence Matrix
2.Transpose of Bus incidence Matrix
3.Oriented Graph
4. Calculation of Yprimitive
5.Multiplication of[AT][Y][A]
1.Oriented Graph
2.Bus incidence Matrix
3.Transpose of Bus incidence Matrix
4.Calculation of Yprimitive
5.Multiplication of [AT][Y][A]
1.Bus incidence Matrix
2.Transpose of Bus incidence Matrix
3.Oriented Graph
4.Multiplication of[AT][Y][A]
5.Calculation of Yprimitive
What is the per unit impedance Z(Pu) in a power system
( Z * (MVA)B) / (KVB)2
( 1000 * (KV)B) / √3 IB
( Z * (KV)2 ) / (MVA)B
None of these
Which among these is the connection diagram for line to line faults?
Only a
Only b
Only c
Only d
Which sequence this ?
Positive sequence
Negative sequence
Zero sequence
All
The operator a^2 is
-0.5+j0.866
-0.5-j0.866
-1+j0.5
-1-j0.5
If a positive sequence current passes through a transformer and its phase shift is 30 degrees, the negative sequence current flowing through the transformer will have a phase shift of
30 deg
-30deg
120 deg
-120 deg
The zero sequence impedances of an ideal star-delta connected transformer (star-grounded)
looking from star side is zero and looking from delta side is infinite
looking from star side is zero and looking from delta side is also zero
looking from star side is infinite and looking from delta side is zero
looking from star side is infinite and looking from delta side is zero
What is the value of zero sequence impedance in line to line faults?
Z0 = 1
Z0 = ∞
Z0 = 3 Zn
Z0 = 0
What is the expression for fault current in line to line fault?
If = √3 * (Ea / Z1 + Z2)
If = 3 * (Ea / Z1 + Z2)
If = √3 * (Ea / Z1 + Z2 + Z0)
If = 3 * (Ea / Z1 + Z2 + Z0)
What will be the sum of (IB + IY) in case of line to line fault, if the fault is occurring in the B and Y lines?
∞
0
1
IR
What are the terminal conditions in case of SLG fault, if the fault occurs in the phase A?
Vb = 0, Ia = 0, Ic = 0
Va = 0, Ib = 0, Ic = 0
Va = 0, Ia = 0, Ic = 0
Vb = 0, Ia = 0, Ib = 0
What percentage of faults occurring is single line to ground fault?
50 %
60 %
35 %
70 %
What are the types of unsymmetrical faults?
Single line to ground fault
Double line to ground fault
Line to line fault
All of these
Which among these is the connection diagram, in case of single line to ground fault?
Only a
Only b
Only c
Only d
A transmission line has self and mutual impedances are 0.8 and 0 pu respectively. Find the positive, negative and zero sequence impedances respectively?
0.6, 0.8 and 1.2 pu
0.6, 0.6 and 1.2 pu
0.6, 0.6 and 0.6 pu
0.8, 0.8 and 0.8 pu
For symmetrical network, the neutral current is
zero
infinity
maximum
any of the above
The positive, negative and zero sequence impedances of a transmission line are 0.5,0.5 and 1.1 pu respectively. The self (Zs) and mutual (Zm) impedances of the line will be given by
Zs = 0.7 pu, Zm =0.2 pu
Zs = 0.5 pu, Zm =0.6 pu
Zs = 0.6 pu, Zm =0.5 pu
Zs = 0.2 pu, Zm =0.7 pu
If all the sequence voltages at the fault point in a power system are equal, then the fault point is a
LLL
LL
LG
LLG
The zero sequence current of a generator for line to ground fault is j3 pu. Then the current through the neutral during the fault is
j3 pu
j1 pu
j9 pu
j6 pu
Which of the following statement is/are true?Zn
The neutral grounding impedance Zn appears as 3Zn in zero sequence equivalent circuit
The neutral grounding impedance Zn appears as Zn in zero sequence equivalent circuit
both 1 and 2
nether 1 nor 2
Various power system faults in increasing order of severity are
LLLG,LLG,LG,LL
LL,LG,LLLG,LLG
LLG,LLLG,LL,LG
LG,LL,LLG,LLLG
Which of following are used to reduce short circuit fault currents
Resistors
Capacitors
Reactors
Parallel combination of all these
Shunt reactors are connected with transmission lines for
Limiting fault current
Absorbing reactive power
Absorbing high voltage surges
Limiting fault current
Minimum faults occur in which of the following power system equipment?
Transformer
Switch gear
CT, PT
Alternator
Possible faults that may occur on a transmission line are
- 3-Phase fault
- L-L-G fault
- L-L fault
- L-G fault
The decreasing order of severity of the faults from the stability point of view is
1-2-3-4
1-4-3-2
1-3-2-4
1-3-4-2
write the formula of Per Unit Value =
(a)
The most common faults that occur in the power system network are
line to line (L-L) fault
double line to ground (LL-G) fault
line to ground (L-G) fault
line to line to line to ground (L-L-L-G) fault
There are mainly two types of faults in the electrical power system. Those are symmetrical and unsymmetrical faults.
line to line to ground (L-L-L-G) & line to line to line (L-L-L) faults
line to ground (L-G) fault & line to line to line (L-L-L) faults
line to line (L-L) and double line to ground (LL-G) faults
line to ground (L-G) fault, line to line (L-L) fault and double line to ground (LL-G) faults
which type of fault is more severe Asymmetrical or Symmetrical fault (a)
why we study the subject power system analysis
To find the fault in the Power System
To know the fault behavior in Power system
To Design the Protection of power System
To know the system behavior, Design the Protection, load flow, stability of the system & future planning of the System.
How many grids we have in india?
5
4
1
2
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
3.5 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
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
4.6 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]
4.9 (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)
What is the value of zero sequence impedance in line to line faults?
Z0 = 1
Z0 = ∞
Z0 = 3 Zn
Z0 = 0
Zero sequence current can flow from a line in to transformer bank if the winding's are in
Grounded star/delta
Delta/star
Star/grounded star
Delta/delta
What percentage of fault occurring in the power system is line to line fault
5 %
30 %
25 %
15 %
What is the expression for fault current in line to line fault?
If = √3 * (Ea / Z1 + Z2)
If = 3 * (Ea / Z1 + Z2)
If = √3 * (Ea / Z1 + Z2 + Z0)
If = 3 * (Ea / Z1 + Z2 + Z05)
What happens to the value of the fault current in case of SLG fault, if fault impedance is introduced?
The fault current increase
The fault current remains same as in case of SLG fault.
The fault current becomes zero
The fault current is reduced
What are the terminal conditions in case of SLG fault, if the fault occurs in the phase A?
Vb = 0, Ia = 0, Ic = 0
Va = 0, Ib = 0, Ic = 0
Va = 0, Ia = 0, Ic = 0
Vb = 0, Ia = 0, Ib = 0
What are cross country faults?
A fault occurring at any point of the power system
Two or more faults occurring simultaneously on the power system
Line to line fault
All of these
What is the fault current expression in case of LLG faults?
If = 3 Ia1
If = 0
If = 3 Ia0
If = Ia1
The load current in short circuit calculation is neglected because
1. Short circuit current much larger than load currents
2. Short circuit current out of phase with load currents
1 and 2
1 or 2
1 alone
2 alone
