Question

A string of 6 suspension insulators is to be fitted with guard ring. The pin to earth capacitances are equal to C. what are the values of line to pin capacitances to have uniform distribution over the string ?

Answer 1

In order to have the uniform voltage distribution across the string the suspension insulators are often fitted with the guard ring and the capacitances of each of these links is given by the formula

  

where , C_p = Capacitance of the pth link

p= number of the link from top

n = total number of insulators

As here are 6 insulators so the number of linking capacitances will be 5 consider the diagram below :

The capacitance of each link can be calculated by above formula;

So

Capacitance of 1st link C₁ = 1 *C/(6-1) = C/5 ; { p =1, n=6}

Capacitance of 2nd link C2 = 2*C/(6-2) = C/2 ; {p =2 ,n =6}

Capacitance of 3rd link C3 = 3*C/(6-3) = C  ; {p =3 ,n =6}

Capacitance of 4th link C4 = 4*C/(6-4) = 2C ; {p =4 ,n =6}

Capacitance of 5th link C5 = 5*C/(6-5) = 5C ; {p =5 ,n =6}

So the value of line to pin capacitances to have uniform voltage distribution across the string is C/5 , C/2 , C , 2C , 5C.