Creepage is a small conductive current between two conductors through an intermediate surface and is usually not a problem as long as it does not lead to insulation failure.
But corona is an electromagnetic phenomenon related to electric discharge inside an ionized gas, which is accompanied by light and sound. The nature of corona currents is the same as the displacement current seen in electric capacitors and is different from the transfer currents caused by creep.
It seems that a difference should be made between the creep current on the surface and the leakage current inside the insulation, which leads to its failure in the long run.
The first is created in a gaseous environment like corona, but the surface contamination of the insulation makes it easier to pass, but the second is mostly created in a solid or liquid environment; So the question of gas ionization is not discussed in it.
The phenomenon of creeping current occurs when we see dirt or dust on the surface of used insulators. When there is dust on the insulator, the electron closes its path on the surface of the conductor, and by moving on the insulator, it reaches the ground point and wastes some current. On the other hand, when it rains, it is mixed with the dust and the current path increases.
However, this low current can cause the insulator to corrode and damage it, so in order to fix it, the insulators are made into logs or cleaned from time to time that this creeping current does not decrease. Of course, the corona phenomenon is based on the emission of electrons in the air, the collision with the air electrons and the transfer of energy to the air, which is similar to light and sound; In order to eliminate corona, bundling and anti-corona are used in posts.
