PRESENTED BY
RAHUL VISWAM
SHILPA.K.M
SIJIN SIVADASAN
SREEDEVI.K.P
SREEDEVI MADHAVAN

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introduction
Stability :
Ability to return to normal or stable operation
Transient stability:
Ability to remain stable for large disturbance .
Determines whether or not synchronism is maintained.
Disturbances:
Switching of heavy loads
Switching of long transmission line
Change in speeds of rotor
Changes in power angle
Loss of large loads.
Need for power flow studies
Involves determination of
1. magnitude and phase angle of voltage at each bus.
2. active and reactive power flow
Give information about line and transformer loads.
Necessary for planning, economic scheduling, future expansion and control of existing system
Types of buses
Load Bus (PQ bus)
A bus without any generators connected to it.
the real power and reactive power are known.
Generator Bus (PV bus)
a bus with at least one generator connected to it
the real power generated PG and the voltage magnitude |V| is known.
Slack Bus (VQ bus)
one arbitrarily-selected bus that has a generator.
the only bus at which the system reference phase angle is defined
Problem description
Gauss-Seidel method
Iterative algorithm for obtaining load flow solution.
Repeats till the solution converges within the accuracy
Equations used in G-S method:
Magnitude of voltage,
Vp(k+1)=1/Ypp [ (Pp-jQp)/(Vpk) -∑Ypq Vq(k+1)-∑Ypq Vqk ]
Phase angle of voltage,
p(k+1) = tan-1 [Im. Part of Vp(k+1) /Re part of Vp(k+1) ]
Introduction to matlab
Refers to Mathematical Laboratory.
Numerical computing environment.
 fourth-generation programming language.
 Developed by MathWorks.
  Simulink adds graphical multi-domain simulation and Model-Based Design for dynamic and embedded systems.
 Allows interfacing with programs written in other languages, including C, C++, Java, and Fortran.
Power flow programs – HadI SAADAT TOOL BOX
Program for G-S method is
lfgauss : designed for direct use of load and generation in MW and Mvar, busvoltage in p.u
and angle in degree.
lfybus : converts impedence to admittance
busout : produces bus output result in tabulated form
lineflow : designed to display active and reactive power flow.
eacfault : for obtaining power angle curve before,during ,after the fault clearence.
problem
Design a configuration plan for power system in Happy Island shown in figures below. Run load flow for transmission system that is designed. Using suitable software program conduct the power flow analysis of system. Analyze the transient stability when there is a transient fault in the midpoint of the line between buses 3 and 4.
location
System description
Numbers 1 to 5 represents the load generation points.
The bus data in table 1 list values for P,Q and V at each bus for base case.
Parameters of all power generation and capacitor in table 2.
The transmission lines length from point to point in the system in table 3.
Transmission line parameters in table 4.
Voltage limit of ±5% of normal and thermal limits of 100MVA for all lines.
PROBLEM ANALYSIS
Basemva=100; accuracy=0.001; accel=1.8; maxiter=100;
% 5-BUS TEST SYSTEM (American Electric Power)
% Bus Bus Voltage Angle ---Load---- -------Generator----- Static Mvar
% No code Mag. Degree MW Mvar MW Mvar Qmin Qmax +Qc/-Ql
busdata=
[
1 1 1.04 0.0 65.0 30.0 0.0 0.0 -999 999 40
2 0 1.0 0.0 115.0 65.0 0.0 0.0 -60 150 0
3 2 1.02 0.0 70.0 40.0 180.0 0.0 -20 50 0
4 0 1.0 0.0 85.0 40.0 0.0 0.0 0 0 0
5 0 1.0 0.0 70.0 30.0 0.0 0.0 0 0 0
];

% Line code
% Bus bus R X 1/2 B 1 for lines
% nl nr p.u. p.u. p.u. > 1 or < 1 tr. tap at bus nl
linedata=
[ 1 2 0.042 0.167 0.0 1
1 3 0.026 0.104 0.0 1
1 4 0.133 0.531 0.0 1
1 5 0.013 0.125 0.0 1
2 3 0.013 0.125 0.0 1
2 4 0.115 0.4602 0.0 1
2 5 0.08397 0.335 0.0 1
3 4 0.08391 0.3346 0.0 1
3 5 0.0525 0.209 0.0 1
4 5 0.0629 0.2509 0.0 1
];

lfybus % form the bus admittance matrix
lfgauss % Load flow solution by Gauss-Seidel method
busout % Prints the power flow solution on the screen
lineflow % Computes and displays the line flow and losses
RESULT
Line Flow and Losses
--Line-- Power at bus & line flow --Line loss-- Transformer
from to MW Mvar MVA MW Mvar tap

1 167.888 167.248 236.977
2 60.463 46.521 76.289 2.260 8.986
3 17.262 45.673 48.827 0.573 2.292
4 26.015 18.816 32.106 1.268 5.061
5 64.128 56.450 85.435 0.877 8.436
2 -115.000 -65.000 132.098
1 -58.203 -37.534 69.256 2.260 8.986
3 -60.339 -26.166 65.768 0.631 6.066
4 7.677 3.741 8.540 0.094 0.377
5 -4.194 -5.286 6.748 0.043 0.171
--Line-- Power at bus & line flow --Line loss-- Transformer
from to MW Mvar MVA MW Mvar tap
3 110.000 7.553 110.259
1 -16.689 - 43.381 46.481 0.573 2.292
2 60.969 32.232 68.965 0.631 6.066
4 34.277 14.702 37.297 1.191 4.749
5 31.517 4.161 31.791 0.541 2.155
4 -85.000 - 40.000 93.941
1 -24.747 -13.755 28.313 1.268 5.061
2 -7.583 -3.365 8.296 0.094 0.377
3 -33.086 -9.953 34.551 1.191 4.749
5 -19.593 -12.817 23.412 0.410 1.635
--Line-- Power at bus & line flow --Line loss-- Transformer
from to MW Mvar MVA MW Mvar tap
5 -70.000 -30.000 76.158
1 -63.251 -48.015 79.411 0.877 8.436
2 4.237 5.457 6.909 0.043 0.171
3 -30.976 -2.006 31.041 0.541 2.155
4 20.002 14.452 24.677 0.410 1.635

Total loss 7.888 39.926
Calculation of transient stability
EI Xt=0.2 1 XL1 =0.515 2 V=1.0
З  Xid =0.3 XL2 =0.335
PROGRAM:
Pm =0.8; E=1.17; V=1.0;
X1=0.76; X2=1.8; X3=0.76;
eacfault(Pm ,E ,V, X1, X2, X3)
RESULT
To find tc enter Inertia Constant H, (or 0 to skip) H = 5
Initial power angle = 31.309
Maximum angle swing = 148.691
Critical clearing angle = 77.863
Critical clearing time = 0.232 sec.