Chapter 33 Protection of Generators

Example 33_1 pgno:624

In [5]:
from math import sqrt
v=11e3/sqrt(3);
v=round(v);
r=5e6;
per=20;
i=r/(3*v);
i=round(i);
i0=i*25/100;
R=per*v/(i0*1000);
R=round(R*100)/100;
print"the resistance to be added=ohms",R

the resistance to be added=ohms 1.94

Example 33_2 pgno:625

In [6]:
from math import sqrt
v=10e3/sqrt(3);
R=10.;
i=1.;
ct=1000./5.;
ip=i*ct;
per=R*ip*100./v;
p=10.;
res=p/100.*v/ip;
print"the percentage of unprotected winding=percent",100-(per)
print"Resistance for 90percent winding protection=ohms",res

the percentage of unprotected winding=percent 65.3589838486
Resistance for 90percent winding protection=ohms 2.88675134595

Example 33_3 pgno:625

In [7]:
from math import sqrt
per=.2;
r=10e6;
R=7;
v=11e3;
i=r/(sqrt(3)*v);
i=round(i);
i0=per*i;
v=v/sqrt(3);
p=R*i0/v*100;
p=round(p*10)/10;
print"percentage of unprotected winding for earth fault=percent",p

percentage of unprotected winding for earth fault=percent 11.6

Example 33_5 pgno:626

In [8]:
from math import sqrt
i=200.;
c=.1;
v=11e3/sqrt(3);
per=.15;
x=per*v/(i);
ru=c*x;
vi=v*c;
y=vi/i;
r=sqrt((y**2)-(ru**2));
r=round(r*100)/100;
print"the neutral earthing resistance=ohms",r

the neutral earthing resistance=ohms 3.14