Why does the Hipot test site have short circuit in the iron core?

High voltage test transformer (hipot tester) test field often occurs fault conditions, and the most common fault is the formation of core short circuit, the formation of core short circuit causes:

(1) The conductive suspended matter forms a conductive bridge under the action of the electromagnetic field of the transformer, so that the iron core and the tank wall or tank bottom are short-circuited.

(2) Manufacturing transformer or core repair, the quality of the selected silicon wafer is questionable. If rough and not lubricated, cold-rolled silicon insulating paint is scattered, and the insulating film with poor adhesion of hot-rolled silicon oxide will fall off. A short circuit is formed between several layers to form a multi-point ground.

(3) During the construction of the transformer oil tank and radiator, the welding slag is not completely cleaned, and in the long-term strong oil circulation, it is gradually brought out by the oil flow, and the iron core and the oil tank wall are short-circuited.

(4) The core processing technology is not suitable. Such as debris replacement, the gas released in the splint, sandwiched with coarse non-metallic particles or hard non-metallic particles, the pressure after lamination used to be a small hole, the other wall is a small bump, stacking will destroy the coating, forming a short circuit between the plates.

(5) Stacking errors. The accumulation coefficient is too large, so that the pressure is too large, and the insulation between the films is destroyed.

(6)Operational errors. The transformer permanently exceeds the nameplate quantitative use of insulation sheets for aging; Normal patrol detection is not enough, so that the core part is seriously overheated, the insulation sheet is damaged, and a multi-point ground is formed. Moreover, during the construction or maintenance of the transformer, the wire brush, wire rope lifting and large broken non-metallic wire are erected under the action of electromagnetic field, forming a short circuit between the iron core and the bottom of the tank.

(7) Water enters in the transformer, so that the insulation pad at the bottom of the iron core is damaged by the core or screw insulation, resulting in a sharp drop in the core insulation and forming a multi-core ground.