(1) The iron core touches the shell and clamps. After installation, due to negligence, the stabilizing (positioning) nails on the top cover of the fuel tank were not turned over or removed, causing the iron core to collide with the tank shell; the iron core clamp limbs touched the iron core column; silicon steel sheet The warpage touches the limbs of the clamp; the cardboard between the foot of the clamp under the iron core and the iron yoke falls off, and the foot touches the silicon steel sheet; the thermometer seat cover is too long to collide with the clamp or the iron yoke or core column, etc.

(2) The core bolt steel seat sleeve is too long and the silicon steel sheet is shorted.

(3) There is a foreign body in the fuel tank, which makes the silicon steel sheet a local short circuit. For example, a 31500/110 type power transformer in a Shanxi substation has multiple grounding of the iron core, and the hanging cover finds a screwdriver with a top handle between the clamp and the iron yoke; another substation has a 60000/22O type The power transformer hanging cover inspired the existing 120mm long copper wire; there is also a transformer substation 120000/220 type power transformer hanging cover after finding a pot between the lower clamp and the iron yoke; another example is a transformer in the northeast The core of a large power transformer in the power station was grounded at multiple points. Inspection of the hanging cover found that there were three sections of zigzag steel wires at the bottom of the fuel tank. The diameter of the steel wires was about 0.31mm, and the lengths were 25, 28, and 31mm respectively.

(4) Moisture or damage to the core insulation, such as deposits of sludge and moisture at the bottom, decrease in insulation resistance, moisture or damage to the clip insulation, shim insulation, and iron box insulation (cardboard or wood block), etc., resulting in more high resistance of the core Grounded.

(5) The bearings of the submersible pump are worn, and the metal powder enters the oil tank and accumulates at the bottom. Under the action of electromagnetic gravity, a bridge is formed, which connects the lower rail with the foot or the bottom of the box, resulting in multiple grounding.

(6) Poor operation and maintenance, not scheduled maintenance