Factors affecting of corona effect:
The phenomenon of corona is affected by the physical state of the atmosphere as well as by the conditions of the line.
Atmosphere:As corona effect is produced due to ionsiation of air surrounding the conductors, therefore, it is affected by the physical state of atmosphere.
Spacing between conductors :If the spacing between the conductors is made very large as compared to their diameters, there may not be any corona effect.It is because larger distance between conductors reduces the electro-static stresses at the conductor surface, thus avoiding corona formation.
Conductor size :The corona effect depends upon the shape and conditions of the conductors. The rough and irregular surface will give rise to more corona effect. Because, unevenness of the surface decreases the value of breakdown voltage.Thus a stranded conductor has irregular surface and hence gives rise to more corona that a solid conductor.
Line voltage :If line voltage is low, there is no change in the condition of air surrounding the conductors and hence no corona is produced.However, if the line voltage has such a value that electrostatic stresses developed at the conductor surface make the air around the conductor conducting, then corona is formed.
Methods of Reducing Corona Effect
- corona effects are observed at a working voltage of 33 kV or above.
- Therefore, careful design should be made to avoid corona on bus-bars rated for 33kV and higher voltages.
- otherwise, highly ionised air may cause flash-over in the insulators or between the phases, causing considerable damage to the equipment.
The corona effects can be reduced by the following methods :
- By increasing conductor spacing : By increasing the spacing between conductors, the voltage at which corona occurs is raised and hence corona effects can be eliminated. However, spacing cannot be increased too much otherwise, the cost of supporting structure may increase to a considerable extent.
- By increasing conductor size: the voltage at which corona occurs is raised and hence corona effects are considerably reduced.This is one of the reasons that ACSR conductors which have a larger cross-sectional area are used in transmission lines.
- Using Bundled conductors: use if bundled conductors produced a less resistance and thats way losses are reduced.
- Corona effect reduces the effects of transients produced by surges.
- System performance is improved.
- The maximum electrostatic stress is reduced.
- power loss in increased.
- Corrosion on the conductor produced due to chemical action.
- Third harmonics are produced.
If any query or suggestion about Methods of Reducing Corona Effect please comment below or Email on Dipak@electricalidea.com