# By using bundle conductors, the critical voltage for the formation of corona will be

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By using bundle conductors, the critical voltage for the formation of corona will be
1. Remain same
2. Increase
3. Decrease
4. Not occur

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Correct Answer - Option 2 : Increase

There are many advantages of using bundled conductors in transmission lines:

Reduced Reactance:

Due to bundling of conductors the self GMD of the conductors is increased, so reactance of conductors decreases

Reduced Corona Loss:

There is an optimum spacing between sub conductors of a bundled conductor which give minimum gradient on the surface of sub conductors and hence highest critical disruptive voltage and hence reduced corona loss

The power dissipated in the system due to corona discharges is called corona loss. Accurate estimation of corona loss is difficult because of its variable nature. It has been found that the corona loss under fair weather conditions is less than under foul weather conditions. The corona loss under appropriate weather conditions is given below by the Peek’s formula,

${P_C} = \frac{{244}}{\delta }\left( {f + 25} \right){\left( {{E_n} - {E_0}} \right)^2}\sqrt {\frac{r}{D}} \times {10^{ - 5}}\frac{{kW}}{{km}}/phase$

Where Pc – corona power loss

f – Frequency of supply in Hz

δ – Air density factor

En – r.m.s phase voltage in kV

Eo – disruptive critical voltage per phase in kV

r – Radius of the conductor in meters

D – Spacing between conductors in meters