Features of 11kV & 33kV oil-immersed distribution transformer
1. The features of the product structure are:
Core of transformer are made by the high quality cold-rolled grain-oriented silicon steel sheet with laser notch, cutting by the imported world first class cut-into-length production line to ensure less shear burrs, high precision lamination, also inclined by 45° full-seam construction, making the silicon steel sheet rolling direction same as the magnetic flux direction, it can reducing the load loss, load current and noise level.
1.2 HV winding is made with polyvinyl acetal wire enamel wire, layer type, double-sided glue dots paper are used as the layer insulation between layers, it will stick together after dry, so that the HV winding to solidify to a solid after dry. HV winding ampere-turns arranged by our specific technology, it will reduce axial strength during short circuit happen.
1.3 Corrugated tank structure used in the transformer design. The imported corrugated tank production line can produce the corrugated sheet and welding seam automatically, the weld the tank rim and bottom on the welding desk, it will be performed the leakage test after welding process finished one tank by one tank, and a finally leakage test for whole transformer to ensure the quality of sealing.
1.4 The oil will be filling in the transformer under vacuum condition, strictly and advanced technology greatly improved the insulation strength of transformer.
1.5 Lastest invention technology are used on designing of transformer bushing, no pressure pin and plate on the outside, it avoids oil leakage, steel rust and etc, the structure is reasonable and contour artistic.
1.6 Oil level gauge with magnetic plate structure, it can fully isolation the oil tank and air, can ensure the quality of transformer oil not to effect by ultraviolet radiation.
1.7 Bar-type No Circuit Tap Changer used on the transformer design, it is easy to be operated. It can be automatically and quickly switched, and have obviously feeling during switched by hand. Effectively solve the problems of switch as other tap-changer. Client can also add a lock to prevent the non-normal random switching according their requirement.
2. Dyn11:
The comparison of the Dyn11 and Yyn0 vector group:Both Dyn11 and Yyn0 vector group distribution transformers are three-phase three-column type, only the insulation requirements of high-voltage winding of Dyn11 transformer, insulation strength slightly higher than Yyn0, others are all similar. However, still big difference between those two types of transformers.
2.1 Three-column core transformer, the third harmonic flux only can circulate through the tank wall and other parts. Thus,walls and other components will be heated cause by the stray loss. Dyn11 will much better than Yyn0 in this issue.
2.2 Zero sequence impedance of Dyn11 is much smaller than Yyn0, it is conducive to shut off load in LV side when fault grounding happened.
2.3 Dyn11 transformer can be running even the neutral current is equal or more than 75% of phase current. Therefore, the ability to withstand unbalanced load, Dyn11 is greater than Yyn0.
2.4 When one phase fuses in HV side of Dyn11 transformer, the other two-phase load can still run, but Yyn0 can not. So Dyn11 vector group, the neutral potential displacement of LV side will not be affected by the unbalanced load.
2.5 Whether single-phase short circuit in LV side, or three-phase short circuit, the current is no change with the neutral grounding type of Dyn11 transformer.
2.6 Single-phase short circuit current of Dyn11 transformer is approximately equal to three-phase short-circuits current,which is beneficial to fuses choosing. Zero sequence impedance of Yyn0 transformer is greater than the positive and negative sequence impedance, so the single-phase short-circuit current is less than three-phase short-circuit current, it will take some difficult in fuses choosing.