Question Bank
Power System Analysis-2 (17EE71)
Module 01
Load Flow Studies
Dec 2018/Jan 2019
1 With usual notation, prove that 𝑌𝑏𝑢𝑠 = 𝐴𝑇 𝑌𝐴 using singular transformation. 06
For the power system shown in fig. below, obtain 𝑌𝑏𝑢𝑠 using singular
transformation.
2 10
What is load flow analysis? Explain how buses are classified to carryout load
3 06
flow analysis in power system.
For the sample system of fig. below, the generators are connected to all the
4- busses, while loads are at buses 2 and 3. Value of real and reactive powers
are listed in table below. All buses other than slack bus are PQ type.
Bus P (pu) Q (pu) Type of bus
1 -- -- 1.04 ∠ 0 Ref
2 0.5 -0.2 -- PQ
3 -1.0 0.5 -- PQ
4 0.3 -0.1 -- PQ
4 10
June/July 2019
With the help of suitable examples, explain (i) Oriented graph (ii) Tree (iii)
5 05
Cotree
6 With usual notations, show that 𝑌𝑏𝑢𝑠 = 𝐴𝑇 𝑌𝐴 using singular transformation. 05
An oriented graph of a 4-bus power system is shown in fig. below.
Determine the bus admittance matrix, 𝑌𝑏𝑢𝑠 using singular transformation
7 method. Elements numbers and self-impedance of the elements are marked 06
on the diagram in pu. Neglect mutual coupling.
What is load flow analysis? Explain the different types of buses considered
8 during power system load flow. Discuss the significance of slack bus in load 06
flow studies.
Define primitive network. Give the representation of a typical component
9 and arrive at their performance equations in impedance and admittance 04
forms.
One line diagram of a power system is shown in fig. below. Using Gauss-
Seidel method. Determine the complex voltage at Bus-2 at the end of first
iteration. Given that 𝑉1 = 1∠0 pu. 𝑃2 − 𝑗𝑄2 = −5.96 + 𝑗1.46 𝑝𝑢 . |𝑉3 | =
1.02 𝑝𝑢 , 𝑍2 = 0.04 + 𝑗0.06 and 𝑍3 = 0.02 + 𝑗0.03 𝑝𝑢.
10 06
Dec 2019/Jan 2020
Define the following with simple examples: (i) tree (ii) element bus
11 04
incidence matrix.
12 Explain how busses are classified for load flow study. 06
Obtain 𝑌𝑏𝑢𝑠 by singular transformation method for the system having
following data. Take bus 4 as ref bus.
Element No. 1 2 3 4 5
13 06
Bus code (p-q) 1-2 2-3 3-4 1-4 2-4
Admittance (pu) 2 1.5 3 2.5 4
14 What is primitive network? Obtain admittance form of primitive network. 04
15 Explain the method of 𝑌𝑏𝑢𝑠 by singular transformation. 06
For the system shown below, obtain solution of voltage and angle at bus 2
and 3 at the end of first iteration using Gauss-Seidel load flow method. Use
16 06
flat start. Line data is in impedance form.
Aug/Sept 2020
Define the following terms with an example: (i) Oriented graph (ii) Tree (iii)
17 06
Co-tree
Fig. below shows a three-bus power system, using Gauss-Seidel method
determine the bus voltages at the end of first iteration. The values shown are
line impedance in pu. Bus data are given in table.
Generation Load
Bus Voltage
PG (pu) QG (pu) PD (pu) QD (pu)
1 -- -- -- -- 1.05∠00
2 3 -- -- -- 1.0
3 -- -- 4 2 --
18 10
With the help of singular transformation method, determine the bus
admittance matrix 𝑌𝑏𝑢𝑠 for the power system whose oriented graph is shown
below. Elements and self-impedance of the elements in pu are marked on the
diagram. Neglect the mutual coupling.
19 08
Explain the classification of different types of buses considered during power
20 08
system load flow analysis. Discuss the need of slack bus an such analysis.
Prepared By
Var ap ras a d Gaon kar
As s i s t a n t P r o f e s s o r
Dept. of EEE
VDIT Haliyal
Question Bank
Power System Analysis-2 (17EE71)
Module 02
Load Flow Studies (Continued)
Dec 2018/Jan 2019
Draw the flow chart of Newton-Raphson method of load flow analysis in
1 08
polar coordinates
2 Derive expression for all elements of Jacobian matrices on polar form. 08
3 Stating all assumptions, deduce the FDLF model and give flow chart. 10
4 Compare Gauss-Seidel and Newton-Raphson methods of load flow analysis. 06
June/July 2019
Differentiate between NR and GS methods of load flow analysis in respect of
the following: (i) Time per iteration (ii) Total solution time (iii) Acceleration
5 04
of convergence of iterative solution (iv) Adoptability for power system
calculations.
Discuss how the voltage profile is controlled in an interconnected power
6 06
system by (i) Adjusting generator excitation (ii) VAR generators.
Explain the significance and properties of Jacobian matrix of Newton-
7 06
Raphson load flow analysis.
8 Deduce FDLF model clearly stating all the assumptions made. 08
With the help of flow chart explain Newton-Raphson method of load flow
9 08
analysis.
Dec 2019/Jan 2020
What are Jacobian elements? Obtain Jacobian elements for basic equations
10 04
for J1 and J3 only.
11 Give algorithm for Newton-Raphson load flow (NRLF). 06
12 Explain any two methods of control of voltage profile. 06
13 Explain the control of voltage by Tap changing transformer. 04
14 Draw a flow chart for Fast Decoupled Load Flow (FDLF) method. 06
15 Compare load flow methods with standard features. 06
Aug/Sept 2020
Discuss clearly the significance and properties of Jacobian matrix as applied
16 06
to load flow analysis.
Stating all assumptions, deduce the FDLF model. Explain the step by step
17 10
procedure for load flow solution using FDLF method
Discuss the algorithm procedure for load flow analysis using Newton-
18 Raphson’s method in polar coordinates. Mention the conditions under which 10
N-R method is superior over G-S method for load flow analysis.
19 Explain any two methods of voltage control in power system. 06
Prepared By
Var ap ras a d Gaon kar
As s i s t a n t P r o f e s s o r
Dept. of EEE
VDIT Haliyal
Question Bank
Power System Analysis-2 (17EE71)
Module 03
Optimal System Operation
Dec 2018/Jan 2019
1 Deduce the condition for optimal load dispatch considering transmission losses in a system. 06
The operating cost of C1 and C2 in Rs/hr of two generator units each of 100MW rating of a
thermal plants are
𝐶1 = 02𝑃12 + 40𝑃1 + 120 𝑅𝑠/ℎ𝑟
2 𝐶2 = 025𝑃22 + 30𝑃2 + 150 𝑅𝑠/ℎ𝑟 10
(i) Find optimal generation of 2- units for a total demand of 180MW and the corresponding
total cost.
(ii) Saving in Rs/hr in this case, as compared to equal sharing between the two machines.
3 With a usual notation, derive the generalised transmission loss formula and B-coefficients. 08
Calculate the loss coefficient in p.u. and MW-1 on a base of 50MVA for the network shown
below.
𝐼𝑎 = 1.2 − 𝑗0.4 𝑍𝑎 = 0.02 + 𝑗0.08
𝐼𝑏 = 0.4 − 𝑗0.2 𝑍𝑏 = 0.08 + 𝑗0.32
𝐼𝑐 = 0.8 − 𝑗0.1 𝑍𝑐 = 0.02 + 𝑗0.08
𝐼𝑑 = 0.8 − 𝑗0.2 𝑍𝑑 = 0.03 + 𝑗0.12
𝐼𝑒 = 1.2 − 𝑗0.3 𝑍𝑒 = 0.03 + 𝑗0.12
4 08
June/July 2019
Derive an expression for optimal operation of ‘n’ units when a plant considering the effect of
5 06
transmission losses.
What are B-coefficients? For the system shown in fig below, obtain loss coefficients and the
power loss. Take 𝐼1 = 1∟0 𝑝𝑢, 𝐼2 = 0.8∟0 𝑝𝑢, 𝑉3 = 1∟0 𝑝𝑢. Transmission line impedances
𝑍𝑎 = 0.02 + 𝑗0.25 𝑝𝑢, 𝑍𝑏 = 0.03 + 𝑗0.35 𝑝𝑢
6 10
State unit commitment problem. Describe the dynamic programming method for computation
7 07
of optimal unit commitment.
The incremental fuel costs in Rs/MWh for a plant consisting of two units are:
𝑑𝑐1 𝑑𝑐2
= 0.25𝑃1 + 40 = 0.3𝑃2 + 30
𝑑𝑃1 𝑑𝑃2
8 Assume that both units are operating at all times and the total load varies from 40MW to 09
250MW. (i) How will the load be shared for a load of 200MW? What is the corresponding
value of plant incremental cost? (ii) Determine the saving in the fuel cost in Rs/Day for the
optimal scheduling of a total load of 250MW as compared to equal distribution of the same
load between two units.
Dec 2019/Jan 2020
09 Explain the followings: (i) Input-Output curve (ii) Heat rate curve, related to thermal plants. 04
Define unit commitment. Explain Dynamic programming method of Unit commitment
10 06
solution.
With the help of two state model of generator derive probability of availability and
11 06
unavailability in terms of failure rate and repair rate.
The fuel input per hour of plant 1 and plant 2 are given by,
𝐹1 = 0.2𝑃12 + 40𝑃1 + 120 𝑅𝑠/ℎ𝑟 𝐹2 = 0.25𝑃22 + 30𝑃2 + 150 𝑅𝑠/ℎ𝑟
12 04
Determine the economical scheduling neglecting losses for a load of 180MW. Also calculate
cost of production of 180MW for obtained schedule.
Obtain transmission loss coefficients in terms of plant generation capacities for two units
13 06
delivering a load.
Obtain economic scheduling for a system having transmission losses and no limit on
14 06
generators.
Aug/Sept 2020
Derive an expression for economical load schedule for an n-plant system neglecting the
transmission losses and hence show that plant incremental cost is given by
𝑏𝑖
𝑃𝐷 +∑𝑛 𝑖−12𝑐
15 𝑖 10
𝜆= 𝑛 1
∑𝑖=1
2𝑐𝑖
where, PD is load demand in MW, bi and ci are coefficients of cost functions.
16 State unit commitment problem. In brief explain dynamic programming method. 06
Write down the transmission loss formula. Obtain the loss coefficient formula for a system
17 consisting of two generating plants for suppling several loads through a transmission line 08
network.
Briefly explain the two state generator models. With usual notation derive the expression for
18 08
availability and unavailability in terms of failure and repair rate.
Prepared By
Var ap ras a d Gaon kar
As s i s t a n t P r o f e s s o r
Dept. of EEE
VDIT Haliyal
Question Bank
Power System Analysis-2 (17EE71)
Module 04
Optimal System Operation (continued)
Dec 2018/Jan 2019
Discuss the problem formulation and solution procedure of optimal scheduling for hydro
1 10
thermal plant.
2 Draw the flow chart of optimal load flow solution. 06
3 Explain power system static security level classification. 08
4 Define (i) power system reliability (ii) power system security. 08
June/July 2019
Discuss clearly the problem formulation and solution procedure of optimal scheduling for
5 08
hydro-thermal plants.
What do you understand by the reliability of a power system? Explain the state space model
6 08
used for power system reliability evaluation.
7 Describe the power system security assessment and modelling for contingency analysis. 08
8 Explain with the help of a flow chart, the optimal load flow solution. 08
Dec 2019/Jan 2020
Explain the followings:
09 (i) Loss of Load Probability (LOLP) 04
(ii) Frequency and duration of state (FAD)
10 Explain hydro-thermal scheduling in brief with mathematical formula. 06
With the help of Bath tube curve, explain different failures in a system and initiatives to
11 06
reduce the failures.
12 List and explain advantages of maintenance scheduling. 04
13 Explain system security state with a block diagram. 06
Explain the followings:
14 (i) Generator shift distribution factor. 06
(ii) Line outage distribution factor.
Aug/Sept 2020
Explain problem formulation and solution procedure of optimal scheduling for hydrothermal
15 09
plants.
Explain the state space method used for power system reliability evaluation. Explain Loss Of
16 07
Load Probability (LOLP)
17 Write a flow chart for the optimal load flow solution. 08
Define energy management system. Explain the major functions that are carried out in an
18 08
energy control centre of power system security.
Prepared By
Var ap ras a d Gaon kar
As s i s t a n t P r o f e s s o r
Dept. of EEE
VDIT Haliyal
Question Bank
Power System Analysis-2 (17EE71)
Module 05
Symmetrical Fault Analysis & Power System
Stability
Dec 2018/Jan 2019
Derive the generalised algorithm for finding the elements of bus impedance matrix when a
1 08
branch is added to the partial network.
For the three-bus network shown in fig below build Zbus
2 08
3 Explain the numerical solution of swing equation. 08
Explain clearly the steps involved in solving power system stability solution of swing
4 08
equation using Range-Kutta method.
June/July 2019
Derive the generalized expression for finding the diagonal elements of bus impedance matrix
5 08
when a branch is added to the partial network.
6 Discuss the steps for determining multimachine stability. 08
With the necessary equations, explain the solution of swing equation by point by point
7 08
method. Mention the assumptions made.
Form Zbus using building algorithm of the power system shown below. Self impedance of
elements are marked on the diagram. Add elements in the order specified. Neglect mutual
coupling. Take bus-1 as reference.
8 08
Dec 2019/Jan 2020
09 Explain the Zbus algorithm for a link addition to the partial network with no mutual coupling. 08
10 Explain solution of swing equation by Runge-Kutta order 4 method. 08
Obtain Zbus technique for the system shown below. All values are in pu (impedance). Take
bus ‘0’ as reference bus. Add the elements in the order ref bus to bus 1, ref bus to bus 2 and
lastly bus 1 to bus 2.
11 08
12 Explain solution of swing equation by point by point method. 08
Aug/Sept 2020
Form Zbus using building algorithm of the power system shown in fig.1. Take element-3 as
link and bus-1 as reference bus.
Element No. 1 2 3
Self-Impedance j0.5 j0.25 j0.3
13 08
14 Explain point by point method of solving the swing equation. 08
Obtain the generalized algorithm expression for bus impedance matrix elements when a link
15 08
is added to the partial network. Also discuss the special cases.
Illustrate clearly the steps involved solving swing equation using Runge-Kutta method for
16 08
transient analysis.
Prepared By
Var ap ras a d Gaon kar
As s i s t a n t P r o f e s s o r
Dept. of EEE
VDIT Haliyal
