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//Book - Power system: Analysisi & Design 5th Edition
//Authors - J. Duncan Glover, Mulukutla S. Sarma, and Thomas J.Overbye
//Chapter-9 ;Example 9.3
//Scilab Version - 6.0.0; OS - Windows
clc;
clear;
Xn=0.05 //motor neutral is grounded through reactance in per unit
Sb=100 //Base value of system in MVA
Vb=13.8 //Base voltage of system in kV
Vf=1.05 //Prefault voltage in per unit
Z0=%i*0.250 //Zero sequence impedance in per unit
Z1=%i*0.13893 //Positive sequence impedance in per unit
Z2=%i*0.14562 //Negative sequence impedance in per unit
Zf=0 //Fault through impedance in per unit
If0=Vf/(Z0+Z1+Z2+(3*Zf)) //sequence line to ground fault current in per unit
If1=If0;If2=If0; // Since If0=If1=If2
If=[If0;If1;If2]
Isf=3*If0 //subtransient fault current in per unit
Ib2=Sb/(Vb*sqrt(3)) //base current at bus 2 in kA
Ib22=Isf*Ib2
Vsf=[0;Vf;0]-([Z0 0 0;0 Z1 0;0 0 Z2]*If) //sequence componenets of the voltages at the fault in per unit
a=exp(%i*(120)*(%pi/180)); //operator a
Vlg2=[1 1 1;1 (a^2) a;1 a (a^2)]*Vsf //line to ground voltages at faulted bus 2 in per unit
for i=1:3 //This loop is included to avoid discrepancies in angle values when the voltage value is near to zero or zero
if abs(Vlg2(i))<1e-6 //For example, atand(0,0) gives 0 degree and atand(0,-0) gives 180 degree
Vlg2(i)=0;
end
end
printf('The magnitude of subtransient at bus 2 in is %.4f kA and its angle is %.4f degrees\n',abs(Ib22),atand(imag(Ib22),real(Ib22)));
disp(abs(Vlg2),'The magnitude of line to ground voltages at faulted bus 2 in per unit is:');
disp(atand(imag(Vlg2),real(Vlg2)),'The angle of line to ground voltages at faulted bus 2 is :');
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