Impact of Natural Calamities
1. Heavy lightning: If the HTLAs (HT Lightning Arrestors) fail to divert direct lightning strikes or surges since of discontinuity in the earthing system, the HV winding can fail because of surge voltage or the HT Lightning Arrestor itself might burst.
2. Bushing flashover: Dust and chemicals carried along with air and deposited on the bushings decrease the electric leakage distance and cause flashover. To prevent this, the bushings (both HT and LT) should be cleaned properly at regular intervals. Therefore, cotton waste shall not be used for cleaning, since this might cause scratches within the bushing and subsequently lead to flashover of bushing.
3. Failure due to contact with birds and other animals: To prevent failure of the distribution transformer because of a squirrel crossing it or because of birds sitting on it, the HT/LT bushing and HT/LT jumper leads from the bushing should be covered along with yellow tape insulation. That yellow tape insulation will also implies the overloaded operation of the transformer through the change of color of the tape from Yellow to Black.