WHAT A DISTRIBUTION TRANSFORMER IS FOR
A distribution transformer sits between the medium-voltage feeder and the building it serves. It takes the line voltage - 6, 10, 22 or 35 kV for our range - and steps it down to 0.4 kV for the switchboard. Everything after that point is someone else's job. Everything before it is what this page covers.THE FOUR NUMBERS THAT SETTLE THE ORDER
Every XIAOPAI distribution transformer is quoted against four parameters, and we ask for all four before we price anything. Rating (kVA). The apparent power the unit must carry, taken from the calculated load rather than a guess. Distribution transformers are standardised in a 50 to 2,500 kVA band, and the correct value falls out of the load study. Voltage class. The primary follows the feeder - 6, 10, 22 or 35 kV. The secondary is 0.4 kV. Get either side wrong and the unit cannot be connected at all. Cooling type. Oil-immersed or dry-type. This is a site decision as much as a technical one: it changes the enclosure, the fire risk and the maintenance burden. Impedance and vector group. Quoted together, because they set how the unit behaves under fault and how it joins the network. Both are matched to the drawings approved for the site.
OIL-IMMERSED OR DRY-TYPE
XIAOPAI manufactures both families, so the choice is made on the site, not in the catalogue. The oil-immersed range - S9/10/11/13/20/22 - is a sealed design with a corrugated tank wall. The grain-oriented silicon-steel core uses a step-lap build; the windings are concentric coils with corrugated oil ducts, and the unit is filled under vacuum so moisture and oxygen never sit in the oil. The tap changer is off-circuit, which means the supply is disconnected before a tap is changed. This family suits outdoor substations and utility networks. The dry-type range - SC(B)9/10/11/12/13 - is cast in epoxy resin. Because the coils are encapsulated, the unit is non-flammable, fire-resistant and maintenance-free, and it can be installed directly inside the load centre. This family suits indoor, urban and fire-sensitive sites where an oil tank would not be welcome. See the oil-immersed transformer and dry-type transformer product pages for the two families.VOLTAGE CLASS: 35 KV DOWN TO 0.4 KV
The 35 kV rating is the workhorse of the range, and 0.4 kV is the standard low-voltage output. The primary side follows the feeder - 6, 10, 22 or 35 kV - and the tap range on the high-voltage winding lets the ratio be adjusted to the actual network voltage. The tap changer is manual on the oil-immersed units, so the supply is off before anyone touches it.
