{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "CHAPTER 2.14: LIGHTNING AND PROTECTION AGAINST OVERVOLTAGES DUE TO LIGHTNING" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 2.14.1, Page number 382" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "RI_072 = 72000.0 #Charactersistic of lightning arrester\n", "Z_c = 500.0 #Surge impedance(ohm)\n", "V = 500.0 #Surge voltage(kV)\n", "\n", "#Calculation\n", "#Case(a)\n", "V_a = 2.0*V #Voltage at the end of line at open-circuit(kV)\n", "ratio_a = V_a/V #Ratio of voltage when line in open-circuited\n", "#Case(b)\n", "I = V*1000/Z_c #Surge current(A)\n", "R = RI_072/(I)**0.72 #Resistance of LA(ohm)\n", "ratio_b = R/Z_c #Ratio of voltage when line is terminated by arrester\n", "\n", "#Result\n", "print('Case(a): Ratio of voltages appearing at the end of a line when line is open-circuited = %.f' %ratio_a)\n", "print('Case(b): Ratio of voltages appearing at the end of a line when line is terminated by arrester = %.f' %ratio_b)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Case(a): Ratio of voltages appearing at the end of a line when line is open-circuited = 2\n", "Case(b): Ratio of voltages appearing at the end of a line when line is terminated by arrester = 1\n" ] } ], "prompt_number": 1 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 2.14.2, Page number 384" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "rating = 5000.0 #Rating of transformer(kVA)\n", "V_hv = 66.0 #HV voltage(kV)\n", "V_lv = 11.0 #LV voltage(kV)\n", "V = 66.0 #System voltage(kV)\n", "fluctuation = 0.1 #Voltage fluctuations\n", "BIL = 350.0 #BIL for 66kV(kV)\n", "dynamic_ov = 1.3 #Dynamic over-voltage = 1.3*system operating voltage\n", "V_power_freq = 1.5 #Power frequency breakdown voltage of arrester = 1.5*arrester rating(kV)\n", "lower_limit = 0.05 #Margin of lower limit of arrester rating\n", "\n", "#Calculation & Result\n", "V_rating = V*(1+fluctuation)*0.8*(1+lower_limit) #Voltage rating of arrester(kV)\n", "if(round(V_rating,1)==51):\n", " V_rating_choosen = 50.0 #Arrester rating choosen(kV)\n", " V_discharge = 176.0 #Discharge voltage for 50kV arrester(kV)\n", " protective_margin = BIL-V_discharge #Protective margin available(kV)\n", " V_power_frequency_bd = V_rating_choosen*V_power_freq #Power frequency breakdown voltage(kV)\n", " Over_voltage_dynamic = dynamic_ov*V/3**0.5 #Dynamic overvoltage(kV)\n", " if(V_power_frequency_bd>Over_voltage_dynamic):\n", " print('First arrester with rating 50 kV (rms) & discharge voltage 176 kV chosen is suitable')\n", "if(round(V_rating,1)==61):\n", " V_rating_choosen = 60.0 #Arrester rating choosen(kV)\n", " V_discharge = 220.0 #Discharge voltage for 50kV arrester(kV)\n", " protective_margin = BIL-V_discharge #Protective margin available(kV)\n", " V_power_frequency_bd = V_rating_choosen*V_power_freq #Power frequency breakdown voltage(kV)\n", " Over_voltage_dynamic = dynamic_ov*V/3**0.5 #Dynamic overvoltage(kV)\n", " if(V_power_frequency_bd>Over_voltage_dynamic):\n", " print('Second arrester with rating 60 kV (rms) & discharge voltage 220 kV chosen is suitable')\n", "if(round(V_rating,1)==74):\n", " V_rating_choosen = 73.0 #Arrester rating choosen(kV)\n", " V_discharge = 264.0 #Discharge voltage for 50kV arrester(kV)\n", " protective_margin = BIL-V_discharge #Protective margin available(kV)\n", " V_power_frequency_bd = V_rating_choosen*V_power_freq #Power frequency breakdown voltage(kV)\n", " Over_voltage_dynamic = dynamic_ov*V/3**0.5 #Dynamic overvoltage(kV)\n", " if(V_power_frequency_bd>Over_voltage_dynamic):\n", " print('Third arrester with rating 73 kV (rms) & discharge voltage 264 kV chosen is suitable')" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Second arrester with rating 60 kV (rms) & discharge voltage 220 kV chosen is suitable\n" ] } ], "prompt_number": 1 } ], "metadata": {} } ] }