Found along the insulating surface of the discharge phenomenon

In transformer insulation tests, are often able to find along the insulating surface discharge occurs phenomenon. The surface discharge phenomenon in lightning impulse and sensors and other tests are likely to occur. Creeping discharge caused by two main factors: the first one is that there must be a local region of high electric field strength or "dot." Due to the high electric field strength to make it happen  Air circuit breaker  oil free, with the polarity of the charge generated, which is caused by a  Voltage stabilizer  phenomenon roots. The second more important factor is present on the surface of the insulating power of two (i.e., along the material surface and the vertical surface) component, which is the power lines and the insulating material surface having a point of intersection of less than 90 °, the charge to the before the process of moving, the friction  electric meter  of the insulating material, a large amount of heat, carbonization of the insulating material surface, resulting in a so-called creepage traces, as carbonization, creepage traces of black and therefore known as "black marks." .