Practical of Power System Analysis (PSA)

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PRACTICAL WORK BOOK
FOR 14 EL BATCH, 2017
POWER SYSTEM ANALYSIS
MEHRAN UNIVERSITY OF ENGINEERING
& TECHNOLOGY, JAMSHORO.
DEPARTMENT OF ELECTRICAL
ENGINEERING
Edited By: Aneel kumar sidani

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CERTIFICATE
This is to certify that Mr.__________________ bearing the
ROLL NO. 14EL___ of ELECTRICAL ENGINEERING
DEPARTMENT, 1ST
TERM, FINAL YEAR, has carried
out the necessary practical work for POWER SYSTEM
ANALYSIS subject for the year 2017.
DATED: Sir__________________
_____________ (SUBJECT TEACHER)

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Contents
1. Analysis of Three Phase Star Connected system under balanced and
unbalanced loads- - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - -- - -04
2. Demonstration of Single Phase Equivalent of Three phase Star connected
network- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - 06
3. Simulation of three-phase short circuit fault using MATLAB- - - - - - - - - --11
4. Selection of circuit breaker for three-phase short circuit fault- - - - - - - - - -15
5. To analyze the effects of transients in Power System- - - - - - - - - - - - - - - - - 20
6. Simulation of SINGLE LINE to GROUND fault using MATLAB- - - - - - - 24
7. Simulation of LINE to LINE fault using MATLAB- - - - - - - - - - - - - - - - - - 27
8. Simulation of DOUBLE LINE TO GROUND fault using MATLAB- - - - - - 29
9. Determination of bus admittance matrix using MATLAB- - - - - - - - - - - - - - -31
10.Load Flow Calculation of three bus system by Gauss Seidel Method using
MATLAB- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -34

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Department of Electrical Engineering
Mehran University of Engineering & Technology, Jamshoro
Power System Analysis (7Th
Semester final year)
Lab Experiment #01
Name: ______________________________________________ Roll No: ______________________
Score: _______________ Signature of Lab Tutor: ___________________ Date: _________________
Analysis of Three Phase Star Connected system under balanced
and unbalanced loads
Objective: To determine the behavior of current with balanced and unbalanced Star and delta
connected load.
Equipment:
MATLAB
Theory:
In star connection, there is four wire, three wires are phase wire and fourth is neutral
which is taken from the star point. Star connection is preferred for long distance power
transmission because it is having the neutral point. In this we need to come to the concept of
balanced and unbalanced current in power system.
When equal current will flow through all the three phases, then it is called as balanced
current. And when the current will not be equal in any of the phase, then it is unbalanced
current. In this case, during balanced condition there will be no current flowing through the
neutral line and hence there is no use of the neutral terminal. But when there will be
unbalanced current flowing in the three phase circuit, neutral is having a vital role. It will take
the unbalanced current through to the ground and protect the transformer. Unbalanced current
affects transformer and it may also cause damage to the transformer and for this star
connection is preferred for long distance transmission.

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a) Current waveform under balanced star connected load.
b) Current waveform under unbalanced star connected load.

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c) Voltage waveform in star connected load.
In delta system, the terminating end of one winding is connected to starting end of
other and if connection is continued all three winding. In this fashion we get closed loop. The
three supply lines are taken out from three junctions this is called as three phase delta
connection system.
The load can be connected in similar manner. In this experiment we are concerned with
balance and unbalance loads. When load is connected in delta current due to unbalance
loading will circulated in close loop in delta.

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a) Current waveform under balance condition in delta connected load.
b) Current waveform under unbalance condition in delta connected load.

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c) Voltage waveform in delta connected load.
Result under unbalance load
ACTIVE
POWER(KW)
REACTIVE
POWER(KVAR)
CURRENT(A) LOSSES(W)
R Y B R Y B R Y B N R Y B N TOTAL
20 20 20 15 15 15 104.9 104.9 104.9 0 1101 1101 1101 0 3302.6
10 20 20 15 15 15 78.35 103.9 104.3 37.31 613.8 1079 1088 139.2 2920
20 20 20 5 15 15 86.85 106.3 103.5 36.28 754.3 1131 1071 131.6 3087.6
5 10 20 15 15 15 69.58 77.15 102.9 50.9 484.1 595.2 1058 259.3 2396.94
20 20 20 5 10 15 86.2 95.25 104.2 31.62 743.2 907.3 1085 99.98 2835.38

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Lab Experiment #02
Name: ______________________________________________ Roll No: ______________________
Demonstration of Single Phase Equivalent of Three phases Star
connected network
Objective: Measurement of current in star and delta system.
Equipment:
 VARIAC (variable AC power source)
 Variable balanced three phase resistive load
 Connecting leads
 Multi meter
Theory:
If the current in all the phases is same then it is said to be balanced three phase system and it
can convert to its equivalent single phase circuit.
For star connected load: It is easy to take its equivalent circuit.
For delta connected load: It is not easy to take its equivalent circuit therefore first we have
to convert it onto its equivalent star because in delta there is no neutral point but for single
phase we need a neutral wire i.e. we convert delta circuit into its equivalent star circuit.

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Readings:
Single phase Resistance=250ohm Voltage supply=213V Current=0.85A
Three phase:
Voltage L12=390V L23=392V L13=380V
Currents L1=0.7A L20.7A L3=0.6A

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Lab Experiment #03
Name: ______________________________________________ Roll No: ______________________
Simulation of three-phase short circuit fault using MATLAB
Objective: Simulation of three phase short circuit fault using MATLAB.
Equipment:
 Matlab
Theory:
Basically, transients are momentary changes in voltage or currents that occur over a short
period of time. Transients can be generated internally and externally. External generated
transients are known as surges which are mostly caused by the lighting. Internal generated
transients are very common and they occur on switching of loads. Each time when you switch
on load or switch of load you produce transients. Inductive loads are more involved in its
production. Heavy loads because heavy transients and low load causes low transients. These
transients are carried out (travel) by the same wires used for distribution and transmission of
power.
Description of simulation:
This circuit is a simplified model of a 230 kV three-phase power system. Only one phase of
the transmission system is represented. The equivalent source is modeled by a voltage source
in series with its internal impedance (Rs Ls) corresponding to a 3-phase 2000 MVA short
circuit level and X/R = 10. The source feeds a RL load through a 150 km transmission line.
The line distributed parameters modeled by a single pi section (RL1 branch 5.2 ohm; 138 mH
and two shunt capacitances. The load is modeled by a parallel RLC load block.A circuit
breaker is used to switch the load at the receiving end of the transmission line. The breaker
which is initially closed is opened at t = 2 cycles, then it is reclosed at t = 7 cycles. Current
and Voltage Measurement blocks provide signals for visualization purpose.
SIMULATION MODEL:

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3 Phase Model with Fault on Load
3 Phase Model with Fault on Supply
Results:
Current waveform in 3 Phase Short Circuit Fault on load at Substation 1.

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Current waveform in 3 Phase Short Circuit Fault on load at Substation 2.
Current waveform in 3 Phase Short Circuit Fault on Supply at Substation 1.

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Current waveform 3 Phase Short Circuit Fault on supply at substation 2.
CONCLUSIONS:
At Fault on Load at Fault on Supply
R Y B
S1 -1.1e+4 4662 6356
S2 -1.8e+4 7766 1.05e+4
R Y B
S1 -0.001 -0.09 00.9
S2 8.5e-5 -4.2e-5 -4.3e-5

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Lab Experiment #04
Name: ______________________________________________ Roll No: ______________________
Selection of circuit breaker for three-phase short circuit fault
Objective: Selection of Circuit Breaker from Simulation of 3 Phase Fault Using MATLAB.
Equipment:
 Matlab
Theory:
Three phase fault is a condition when all three phases short together, current and
voltage remains in balanced condition, such conditions occurs in three phase short circuit
fault. The purpose of the fault analysis is to determine that what expected could flow into our
system when such type of fault occurs so as to design the system protection scheme and
protect of system equipment because it terms of severity this fault is more severe.
That is reason we do analysis to select the proper ratings of the circuit breaker to isolate our
system as quick as possible. Because during three phase short circuit fault system remains in
balanced condition so we do analysis and calculation on single phase because rest of the
phases will have same magnitude of current and voltages.
In terms of frequency it occurs rarely with 5% frequency of occurrence. The IEC standard
IEC 60909 'Short Circuit Currents in Three Phase Systems' describes an internationally
accepted method for the calculation of fault currents. IEC 60781 is an adaption of the 60909
standard and applies only to low voltage system.

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SIMULATION MODEL:
3 Phase Circuit under Fault condition at Load Side.
3 Phase Circuit under Fault condition at Supply Side

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Results:
3-Ø V on Fault on Load
3-Ø I on Fault on Load

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3-Ø V on Fault on Supply
3-Ø I on Fault on Supply

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CONCLUSIONS:
PHASE CURRENT ON FAULT ON TRIPPING
CURRENTS (10
4
) Phase a Phase b Phase c
ON LOAD SIDE 0.3 -1.3 1.3
ON SUPPLY SIDE 0.3 -1.3 1.3
PHASE VOLTAGE ON FAULT ON TRIPPING
VOLTAGE (104
) Phase a Phase b Phase c
ON LOAD SIDE 1 -1 1
ON SUPPLY SIDE -0.5 -0.8 1.3

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Lab Experiment #05
Name: ______________________________________________ Roll No: ______________________
To analyze the effects of transients in Power System
Objective:
Effect of transients in power system
Equipment:
 Matlab
Theory:
It is customary and convenient to describe a transmission line in terms of its line parameters,
which are its resistance per unit length R, inductance per unit length L, conductance per unit
length G, and capacitance per unit length C. Each of the lines has specific formulas for
finding R, L, G, and C. The line parameters R, L, G, and C are not discrete or lumped but
distributed Transmission lines are usually analyzed by approximating them by a chain of
many 2-port devices. The 2-port elements can be represented by lumped circuits. The
quantities L and C are respectively the inductance and capacitance per unit length of the line.
Description Of simulation:
This circuit is a simplified model of a 132 kV three-phase power system. All 3 phases
of the transmission system are represented. The equivalent source is modeled by a voltage
source (132 kV rms/sqrt(3) or 132 kV peak, 50 Hz) in series with its internal impedance (Rs
Ls) corresponding to a 3-phase short circuit on load side and Rs =0.1 ohms or Ls = 12 mH
.The source feeds a RL load through a 150 km transmission line. Currents through each phase
of the load and current through neutral will be analyzed individually under fault and no fault
condition through two scopes.
SIMULATION MODEL:

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Results:
Neutral current at fault.
Neutral current at no fault.
-

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Load current at fault.
Load current at no fault.

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At no Fault:
ACTIVE
POWER(KW)
REACTIVE
POWER(KVAR)
20 20 20 15 15 15 104.9 104.9104.9 0 1101 1101 1101 0 3302.6
At Fault:
ACTIVE POWER
(KW)
REACTIVE POWER
(KVAR)
20 20 20 15 15 15 104.9 104.9 104.9 0 1101 1101 1101 0 3302.6
CONCLUSIONS:
1. When there is balanced load than there is no neutral currents flowing.
2. When active load on any phase increases, the neutral current increases more as compared
to the increment in reactive load on any phase increases.
When active load on all three phases reduces, the currents in all phases drops more than if the
reactive load on all three phases reduces.

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Lab Experiment #06
Name: ______________________________________________ Roll No: ______________________
Simulation of SINGLE line to GROUND fault using matlab
Objective: To determine the behavior of current with balanced and unbalanced Delta
connected load.
Equipment:
 Matlab
Theory:
Here we have simulation on single line to ground fault occurs their one phase is short
to the ground and the fault the impedance is not zero. When their output waveform shows the
rise of current on L-G fault occur on overhead transmission line.

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SIMMULATIONS
a) Current wave form I generator side for the SLG fault.
b) Current wave form in load side for the SLG fault

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c) Voltage waveform at load side I SLG fault

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Lab Experiment #07
Name: ______________________________________________ Roll No: ______________________
Simulation of line to LINE fault using matlab
Objective: To determine the behavior of current with balanced and unbalanced Delta
connected load.
Equipment:
 Matlab
Theory:
This occurs when two of the three conductors are short circuited. The figure below
shows the line to line fault in an unloaded star connected generator. The fault has occurred on
phase’s b and c:
SIMMULATIONS
a) Current waveform at generator side in LL fault.

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b) Current waveform at load side.
c) Voltage wave form at the load side at the L-L fault

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Lab Experiment #08
Name: ______________________________________________ Roll No: ______________________
Simulation of double line to ground fault using matlab
Objective: To determine the behavior of current with balanced and unbalanced Star
connected load.
Equipment:
 Matlab
Theory:
Now simulation and modelling on double line to ground fault occurs their two
phases is short to the ground. When the magnitude of the faults current line are higher
than the normal input current and the voltage are not change in magnitude and the
fault the impedance is not necessary zero and output waveform shows the gradually
rise of current where 2L-G fault occur on EHV transmission line.
a) Current waveform on load side under DLG fault

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b) Current waveform on generator side under DLG fault
c) Voltage waveform under DLG side

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Lab Experiment #09
Name: ______________________________________________ Roll No: ______________________
Bus Admittance Matrix
Objective: Determination of bus admittance matrix using MATLAB.
Equipment:
 MATLAB
Theory:
In a power system Bus Admittance Matrix represents the nodal admittances of the various
buses. With the help of the transmission line each bus is connected to the various other buses.
Admittance matrix is used to analyze the data that is needed in the load or a power flow study
of the buses. It explains the admittance and the topology of the network.
The amount of current present in the bus can be calculated with the help of formation of the
Admittance matrix. It is expressed as shown below.
In the simplest form the above matrix can be written as shown below.
Where,
 I is the current of the bus in the vector form.
 Y is the admittance matrix
 V is the vector of the bus voltage.

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PROGRAMING
% Bus Admittance Matrix
% Copyright (c) 1998 by H. Saadat.
function[Ybus] = ybus1(zdata)
nl=zdata(:,1); nr=zdata(:,2); R=zdata(:,3); X=zdata(:,4);
nbr=length(zdata(:,1)); nbus = max(max(nl), max(nr));
Z = R + j*X; %branch impedance
y= ones(nbr,1)./Z; %branch admittance
Ybus=zeros(nbus,nbus); % initialize Ybus to zero
for k = 1:nbr; % formation of the off diagonal elements
if nl(k) > 0 & nr(k) > 0
Ybus(nl(k),nr(k)) = Ybus(nl(k),nr(k)) - y(k);
Ybus(nr(k),nl(k)) = Ybus(nl(k),nr(k));
end
end
for n = 1:nbus % formation of the diagonal elements
for k = 1:nbr
if nl(k) == n | nr(k) == n
Ybus(n,n) = Ybus(n,n) + y(k);
else, end
end
end

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RESULT
>> zdata=[0 1 0 0.01
0 2 0 0.10
1 2 0 0.15
2 3 0 0.25]
zdata =
0 1.0000 0 0.0100
0 2.0000 0 0.1000
1.0000 2.0000 0 0.1500
2.0000 3.0000 0 0.2500
>> yb=yBus1(zdata)
yb =
1.0e+02 *
0.0000 - 1.0667i 0.0000 + 0.0667i 0.0000 + 0.0000i
0.0000 + 0.0667i 0.0000 - 0.2067i 0.0000 + 0.0400i
0.0000 + 0.0000i 0.0000 + 0.0400i 0.0000 - 0.0400i

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Lab Experiment #10
Name: ______________________________________________ Roll No: ______________________
Load Flow Calculation of three bus system by Gauss Seidel
Method using MATLAB
Objective: Obtain the power flow solution by the gauss-seidel method using MATLAB.
Example
Figure shows the one line diagram of a simple three bus power system with generators
at buses 1 and 3. The magnitude of voltage at bus 1 is adjusted to 1.05 pu. Voltage magnitude
at bus 3 is fixed at 1.04 p.u with a real power generation of 200 MW. A load consisting of
400 MW and 250 Mvar is taken from bus 2. Line impedances are marked in per unit on a 100
MVA base and the line charging susceptance are neglected. Obtain the power flow solution
by the gauss-seidel method using matlab.

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PROGRAMING
y12=10-j*20;
y13=10-j*30;
y23=16-j*32;
y33=y13+y23;
V1=1.05+j*0;
%format long
iter =0;
S2=-4.0-j*2.5;
P3 = 2;
V2=1+j*0;
Vm3=1.04;
V3=1.04+j*0;
for I=1:10;
iter=iter+1
E2 = V2;
E3=V3;
V2 = (conj(S2)/conj(V2)+y12*V1+y23*V3)/(y12+y23)
DV2 = V2-E2
Q3 = -imag(conj(V3)*(y33*V3-y13*V1-y23*V2))
S3 = P3 +j*Q3;
Vc3 = (conj(S3)/conj(V3)+y13*V1+y23*V2)/(y13+y23)
Vi3 = imag(Vc3);
Vr3= sqrt(Vm3^2 - Vi3^2);
V3 = Vr3 + j*Vi3
DV3=V3-E3
end
format short
I12=y12*(V1-V2); I21=-I12;
I13=y13*(V1-V3); I31=-I13;
I23=y23*(V2-V3); I32=-I23;
S12=V1*conj(I12); S21=V2*conj(I21);
I1221=[I12,I21]
I1331=[I13,I31]
I2332=[I23,I32]
S1221=[S12, S21 (S12+S13) S12+S21]
S1331=[S13, S31 (S31+S32) S13+S31]
S2332=[S23, S32 (S23+S21) S23+S32]

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Reading:
iter =8
V2 =0.9706 - 0.0457i
DV2 = -1.9772e-06 - 1.5855e-05i
Q3 = 1.4614
Vc3 = 1.0400 - 0.0090i
V3 = 1.0400 - 0.0090i
DV3 = -1.0886e-07 - 1.2525e-05i
iter = 9
V2 = 0.9706 - 0.0457i
DV2 = -8.1775e-07 - 6.5578e-06i
Q3 = 1.4616
Vc3 = 1.0400 - 0.0091i
V3 = 1.0400 - 0.0091i
DV3 = -4.5070e-08 - 5.1804e-06i
iter = 10
V2 = 0.9706 - 0.0457i
DV2 = -3.3824e-07 - 2.7125e-06i
Q3 = 1.4617
Vc3 = 1.0400 - 0.0091i
V3 = 1.0400 - 0.0091i
DV3 = -1.8650e-08 - 2.1428e-06i
I1221 = 1.7082 - 1.1308i -1.7082 + 1.1308i
I1331 = 0.3720 - 0.2107i -0.3720 + 0.2107i
I2332 = -2.2828 + 1.6329i 2.2828 - 1.6329i
S1221 = 1.7936 + 1.1874i -1.7096 - 1.0195i 2.1841 + 1.4085i 0.0839 + 0.1679i
S1331 = 0.3906 + 0.2212i -0.3887 - 0.2157i 2.0000 + 1.4618i 0.0018 + 0.0055i
S2332 = -2.2903 - 1.4805i 2.3888 + 1.6775i -3.9999 - 2.5000i 0.0985 + 0.1969i

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