At Xinbian we make the SZ11-M three phase oil immersed transformer for distribution networks. The unit is built around a grain-oriented cold-rolled silicon steel core and a sealed oil tank, and it is supplied with a 10 kV high voltage winding and a 0.4 kV low voltage winding. Our factory is in Gaocheng District, Shijiazhuang, Hebei, and we produce transformers, silicon steel and transformer cores. The SZ11-M is the oil-immersed distribution type, and the notes below describe the construction and the standard range.

Iron Core Construction

The iron core is made of high-permeability grain-oriented cold-rolled silicon steel sheet. It uses a fully oblique seam stacked core, and the core column has a multi-step circular cross section, with the yoke and the column sharing the same cross section. This construction is the base of the magnetic circuit, and the quality of the steel and the stacking method affect the no-load loss and the noise of the finished transformer. The core should be kept dry and free of mechanical damage before assembly, because a bent or contaminated lamination can raise the loss after the unit is energised.

Coils and Tap Changing

The coil assembly uses a corrugated oil passage, a non-immersed paint process and tightening banding. The windings are all concentric coils, and the high voltage winding has taps for the required tap voltage. The taps are led to a tap switch mounted on the cover. The tap must not be changed while the transformer is energised: the power has to be cut off before the tap voltage is adjusted. The tap range for the standard range is plus or minus 4 by 2.5 percent, and the vector group is Yyn0 or Dyn11 depending on the rating and the connection required.

Oil Tank and Sealing

The oil tank is formed from corrugated walls with a sprayed surface and a firm paint film. The corrugated fins act as a cooling surface and as a breathing element: their elasticity compensates for the change in oil volume caused by temperature rise and fall. Because the tank can breathe through the fins, the fully sealed transformer does not need an oil storage cabinet, which reduces the overall height and the oil volume. The transformer is filled by vacuum oil injection during packaging, which removes moisture and keeps the oil out of contact with air.

Standard Ratings

The table covers rated capacities from 200 kVA to 1600 kVA, with a high voltage of 10 kV and a tap range of plus or minus 4 by 2.5 percent, and a low voltage of 0.4 kV. The vector group is Yyn0 or Dyn11. No-load loss, load loss, no-load current, impedance voltage, exterior dimensions and total weight are listed for each rating. For ratings of 500 kVA and below, the load loss above the ramp in the table applies to the Dyn11 group and the load loss below the ramp applies to the Yyn0 group. The buyer should confirm the rating, the vector group and the losses against the project specification.

Installation and Use

An oil immersed transformer is usually installed outdoors on a plinth or in a substation room, with enough clearance for cooling and for access to the tap switch. The foundation should be level and able to carry the total weight, and the cable or busbar connections should be made without strain on the bushings. Before energising, the oil level, the earthing and the protection settings should be checked by the commissioning team. The unit should be inspected at the intervals set by the operator, and any oil leak or unusual noise should be investigated rather than ignored.

Working With Xinbian

Hebei Xinbian Electric supplies oil immersed transformers, silicon steel and transformer cores for power and electrical projects. Our address is Beizhougua Village, Chang'an Town, Gaocheng District, Shijiazhuang City, Hebei Province, China. For a quotation, send the rated capacity, the voltage combination, the vector group, the loss requirement and the destination, and our team will confirm the configuration and the documents you need. You can reach us at export@hbxinbian.com or on 8613931106889.

If you are comparing transformers, ask for the guaranteed no-load loss, load loss, impedance and temperature rise in writing, and compare them on the same basis. Our team will explain the difference between the ratings in plain terms and tell you when a requirement needs to be confirmed by the project engineer. We would rather settle these points before production than correct them on site.