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// A Texbook on POWER SYSTEM ENGINEERING
// A.Chakrabarti, M.L.Soni, P.V.Gupta, U.S.Bhatnagar
// DHANPAT RAI & Co.
// SECOND EDITION
// PART II : TRANSMISSION AND DISTRIBUTION
// CHAPTER 10: POWER SYSTEM STABILITY
// EXAMPLE : 10.24 :
// Page number 306-307
clear ; clc ; close ; // Clear the work space and console
// Given data
x_d = %i*0.2 // Transient reactance of generator(p.u)
P_e = 0.8 // Power delivered(p.u)
V_t = 1.05 // Terminal voltage(p.u)
H = 4.0 // Inertia constant(kW-sec/kVA)
x_t = %i*0.1 // Transformer reactance(p.u)
x_l = %i*0.4 // Transmission line reactance(p.u)
V = 1.0 // Infinite bus voltage(p.u)
f = 50.0 // Frequency(Hz)
// Calculations
x_12 = x_d+x_t+(x_l/2) // Reactance b/w bus 1 & 2(p.u)
y_12 = 1/x_12 // Admittance b/w bus 1 & 2(p.u)
y_21 = y_12 // Admittance b/w bus 2 & 1(p.u)
y_10 = 0.0 // Admittance b/w bus 1 & 0(p.u)
y_20 = 0.0 // Admittance b/w bus 2 & 0(p.u)
Y_11 = y_12+y_10 // Admittance at bus 1(p.u)
Y_12 = -y_12 // Admittance b/w bus 1 & 2(p.u)
Y_21 = -y_12 // Admittance b/w bus 2 & 1(p.u)
Y_22 = y_21+y_20 // Admittance at bus 2(p.u)
x_32 = x_t+(x_l/2) // Reactance b/w bus 3 & 1(p.u)
theta_t = asind(P_e*abs(x_32)/V_t) // Angle(°)
V_t1 = V_t*exp(%i*theta_t*%pi/180) // Terminal voltage(p.u)
I = (V_t1-V)/x_32 // Current(p.u)
E = V_t1+I*x_d // Alternator voltage(p.u)
sine = poly(0,"sin")
P_e1 = 2.0*abs(E) // Developed power(p.u) in terms of sin δ
P_m_P_e = P_e-P_e1*sine
M = 2*H/(2*%pi*f) // Angular momentum
acc = (P_e-P_e1*sine)*2*%pi*f/(2*H) // Acceleration = α (rad/sec^2)
// Results
disp("PART II - EXAMPLE : 10.24 : SOLUTION :-")
printf("\nSwing equation is, %.4f*α = %.1f - %.3fsin δ\n", M,P_e,P_e1)
printf("\nNOTE: Swing equation is simplified and represented here")
printf("\n ERROR: x_d = 0.2 p.u, not 0.1 p.u as mentioned in textbook statement")
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