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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 14: LIGHTNING AND PROTECTION AGAINST OVERVOLTAGES DUE TO LIGHTNING
// EXAMPLE : 14.2 :
// Page number 383
clear ; clc ; close ; // Clear the work space and console
// Given data
rating = 5000.0 // Rating of transformer(kVA)
V_hv = 66.0 // HV voltage(kV)
V_lv = 11.0 // LV voltage(kV)
V = 66.0 // System voltage(kV)
fluctuation = 0.1 // Voltage fluctuations
BIL = 350.0 // BIL for 66kV(kV)
dynamic_ov = 1.3 // Dynamic over-voltage = 1.3*system operating voltage
V_power_freq = 1.5 // Power frequency breakdown voltage of arrester = 1.5*arrester rating(kV)
lower_limit = 0.05 // Margin of lower limit of arrester rating
// Calculation & Result
disp("PART II - EXAMPLE : 14.2 : SOLUTION :-")
V_rating = V*(1+fluctuation)*0.8*(1+lower_limit) // Voltage rating of arrester(kV)
if(round(V_rating)==51) then
V_rating_choosen = 50.0 // Arrester rating choosen(kV)
V_discharge = 176.0 // Discharge voltage for 50kV arrester(kV)
protective_margin = BIL-V_discharge // Protective margin available(kV)
V_power_frequency_bd = V_rating_choosen*V_power_freq // Power frequency breakdown voltage(kV)
Over_voltage_dynamic = dynamic_ov*V/3**0.5 // Dynamic overvoltage(kV)
if(V_power_frequency_bd>Over_voltage_dynamic) then
printf("\nFirst arrester with rating 50 kV (rms) & discharge voltage 176 kV chosen is suitable")
end
elseif(round(V_rating)==61) then
V_rating_choosen = 60.0 // Arrester rating choosen(kV)
V_discharge = 220.0 // Discharge voltage for 50kV arrester(kV)
protective_margin = BIL-V_discharge // Protective margin available(kV)
V_power_frequency_bd = V_rating_choosen*V_power_freq // Power frequency breakdown voltage(kV)
Over_voltage_dynamic = dynamic_ov*V/3**0.5 // Dynamic overvoltage(kV)
if(V_power_frequency_bd>Over_voltage_dynamic)
printf("\nSecond arrester with rating 60 kV (rms) & discharge voltage 220 kV chosen is suitable")
end
else(round(V_rating)==74) then
V_rating_choosen = 73.0 // Arrester rating choosen(kV)
V_discharge = 264.0 // Discharge voltage for 50kV arrester(kV)
protective_margin = BIL-V_discharge // Protective margin available(kV)
V_power_frequency_bd = V_rating_choosen*V_power_freq // Power frequency breakdown voltage(kV)
Over_voltage_dynamic = dynamic_ov*V/3**0.5 // Dynamic overvoltage(kV)
if(V_power_frequency_bd>Over_voltage_dynamic) then
printf("\nThird arrester with rating 73 kV (rms) & discharge voltage 264 kV chosen is suitable")
end
end
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