Answer / rakesh kumar

due to shunt capacitance which is the capaciance between
the metal links of the discs and the supporting tower ther
is an non uniform potential distribution over the various
discs of the suspension insulators in towers , due to this
the unit nearest to the line conductor having the maximum
stress with progressive decrease in the voltage in the
upper units , therefoe if the lowest disc is subjected to a
voltage highr than the maximum sress then iot would
automatically lead to the failure of all other units as
well . hence the uniformn potential distribution is
essential . The steps that can be taken to iprove the
string efficiency include use of longer cross arms, using
capacitance grading and by using graded ring or guard ring .

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