It has been seen that intense corona effects are observed at a working voltage of 33 KV or above. Therefore, careful design should be made to avoid corona on the sub-stations or bus-bars rated for 33 KV and higher voltages otherwise highly ionized 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:
(I) BY INCREASING CONDUCTOR SIZE: 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.
(II) 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 (e.g., bigger cross arms and supports) may increase to a considerable extent.
