a) When transformers are installed in parallel with low-voltage distribution cabinets, the protection level of their enclosures shall not be lower than IP3X, and when installed separately, it shall not be lower than IP2X;
b) There are no spark discharge marks on the surface of the iron core and sleeve;
c) The casing and insulator have no damage or cracks on the outside;
d) The transformer winding casting body has no cracks or attached dirt;
e) There is no serious accumulation of dirt on the surface of the iron core and sleeve;
f) The sound of the transformer is normal.
