Chapter 26: Neutral Grounding

Example 26.1, Page Number: 599

In [1]:
from __future__ import division
import math

#Variable declaration:
f = 50                    #Supply frequency(Hz)
C = 4.5*10**-6              #Line to earth capacitance(F)


#Calculation:
XL = 1/(3*2*math.pi*f*C)                 #ohm


#Result:
print "The reactance of Peterson coil is",round(XL,1),"ohm"

The reactance of Peterson coil is 235.8 ohm

Example 26.2, Page Number: 599

In [4]:
from __future__ import division
import math

#Variable declaration:
l = 200                    #length of transmission line(km)
f = 50                    #Supply frequency(Hz)
c = 0.02*10**-6              #Line to earth capacitance(F/km)
V = 230                    #voltage rating of line(kV)


#Calculation:
C = c*l                    #capacitance of coil(F)
L = round(1/(3*(2*3.14*f)**2*C),2)           #Required inductance of Peterson coil(H)
Vph = round(V*1000/1.732)             #Voltage across Peterson coil(kV)
IF = math.ceil(Vph/(2*3.13*f*L))              #Current through Peterson coil(A)
kVA = Vph*IF/1000               #Rating of Peterson coil



#Calculation:
print "Inductance of Peterson coil is",L,"H"
print "Rating of Peterson coil is",round(kVA),"kVA"

Inductance of Peterson coil is 0.85 H
Rating of Peterson coil is 66397.0 kVA

Example 26.3, Page Number: 600

In [5]:
from __future__ import division
import math

#Variable declaration:
f = 50                      #fequency of supply(Hz)
C = 1.2*10**-6              #line-to-earth capacitance(F)


#Calculation:
#(i) To neutralize capacitance of 100% of the length of the line,
#Inductive reactance of the coilis given by
XL1 = 1/(3*2*math.pi*f*C)           #ohm

#(ii)  To neutralize capacitance of 90% of the length of the line,
#Inductive reactance of the coilis given by
XL2 = 1/(3*2*math.pi*f*0.9*C)       #ohm


#(iii) To neutralize capacitance of 80% of the length of the line,
#Inductive reactance of the coilis given by
XL3 = 1/(3*2*math.pi*f*0.8*C)       #ohm


#Result:
print "(i)  Inductive reactance of the coil to neutralize capacitance"
print "     of 100% of the length of the line is",round(XL1,2),"ohm"
print "\n(ii) Inductive reactance of the coil to neutralize capacitance"
print "     of 100% of the length of 90% of the line is",round(XL2,2),"ohm"
print "\n(iii)Inductive reactance of the coil to neutralize capacitance"
print "     of 100% of the length of 80% of the line is",round(XL3,2),"ohm"

(i)  Inductive reactance of the coil to neutralize capacitance
     of 100% of the length of the line is 884.19 ohm

(ii) Inductive reactance of the coil to neutralize capacitance
     of 100% of the length of 90% of the line is 982.44 ohm

(iii)Inductive reactance of the coil to neutralize capacitance
     of 100% of the length of 80% of the line is 1105.24 ohm

Example 26.4, Page Number: 600

In [6]:
from __future__ import division
import math

#Variable declaration:
r = 0.01                          #radius of conductor(m)
d = 4                             #conductor spacing(m)
V = 132                           #voltage of the line(kV)
f = 50                            #supply frequency(Hz)
l = 200                           #line length(km)


#Calculation:
c = round(2*math.pi*8.885/math.log(d/r),1)*10**-12        #capacitance per unit length(F/m)
C = c*l*1000                         #Capacitance between phase and earth for 200 km line(F)
L = round(1/(3*(2*math.pi*f)**2*C),2)               #required inductance L of the arc suppression coil(H)
IF = V*1000/(10*math.ceil(3**0.5*2*math.pi*f*L/10))          #Current through the coil(A)
kVA = V/3**0.5*IF                     #kVA


#Result:
print "The inductance of the coil is",L,"H"
print "Rating of the coil is",round(kVA),"kVA"

The inductance of the coil is 1.82 H
Rating of the coil is 10060.0 kVA