Insulator String
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1. For a 6 unit insulator string where the capacitance between each link/pin and earth is 0.1 of the self capacitance, the voltage across the lowest unit is 58.29% of the total voltage and the string efficiency is 58.29%. 2. For a 3 unit string where the link/pin capacitances to earth and line are 20% and 10% of the self capacitance, the voltage distribution is 0.31V, 0.303V, 0.387V with an efficiency of 86.13%. With a guard ring increasing the lower link/pin capacitance to 35% of the self capacitance, the voltage distribution is 0.3299V, 0.
![Insulator string Questions
1. I n a 6 unit suspension insulator string, the capacitance between each link and pin and earth is
0.1 of the self capacitance of each unit. Determine the voltage across the lowest unit as a
percentage of the total voltage and also the string efficiency. [58.29%]
2. Find the voltage distribution and string efficiency of a three unit suspension insulator string of a
three unit suspension insulator string if the capacitances of the link pins to earth and to the line
are respectively 20% and 10% of the self capacitance of each unit. If a guard ring increases the
capacitance to the line of lower link pin to 35% of the self capacitance of each unit, find the
redistribution of voltage and string efficiency.
[0.31V, 0.303V, 0.387V, 86.13%; 0.3299V, 0.328887V, 0.34123V, 97.68%]
3. Each conductor of a three phase overhead line is suspendedfrom a cross armof a steel tower by
a string of 4 suspension insulators. The voltage across the second unit is 14.2kV and across the
third 20kV. Find the voltage between the conductors and the string efficiency.
[131.79kV, 62.78%]
4. In a string of three insulator units, the capacitance of each unit is C, from each conductor to
ground is C/3, and from each connector to the line conductor is C/5. Calculate the voltage across
each unit as a % of the total voltage. To what value the capacitance between the connector of
the bottom unit and the line has to be increased by a guard ring to make the voltage across it
equal to that across the next higher unit? [31.5%, 28.3%, 40.196%; 0.6833C]](https://image.slidesharecdn.com/insulatorstring-091206221544-phpapp01/85/Insulator-String-1-320.jpg)
Insulator String
- 1. Insulator string Questions 1. I n a 6 unit suspension insulator string, the capacitance between each link and pin and earth is 0.1 of the self capacitance of each unit. Determine the voltage across the lowest unit as a percentage of the total voltage and also the string efficiency. [58.29%] 2. Find the voltage distribution and string efficiency of a three unit suspension insulator string of a three unit suspension insulator string if the capacitances of the link pins to earth and to the line are respectively 20% and 10% of the self capacitance of each unit. If a guard ring increases the capacitance to the line of lower link pin to 35% of the self capacitance of each unit, find the redistribution of voltage and string efficiency. [0.31V, 0.303V, 0.387V, 86.13%; 0.3299V, 0.328887V, 0.34123V, 97.68%] 3. Each conductor of a three phase overhead line is suspendedfrom a cross armof a steel tower by a string of 4 suspension insulators. The voltage across the second unit is 14.2kV and across the third 20kV. Find the voltage between the conductors and the string efficiency. [131.79kV, 62.78%] 4. In a string of three insulator units, the capacitance of each unit is C, from each conductor to ground is C/3, and from each connector to the line conductor is C/5. Calculate the voltage across each unit as a % of the total voltage. To what value the capacitance between the connector of the bottom unit and the line has to be increased by a guard ring to make the voltage across it equal to that across the next higher unit? [31.5%, 28.3%, 40.196%; 0.6833C]