69kV/50000 kva Step down Transformer

Description

Specifications

Features:

1) Amount of local discharged: The apparent discharge amount is less than 80pC under 1.5 times of rated voltage;

2) Noise: Products of 63MVA and below is lower than 58 dB (AN);

3) Power loss: no-load loss is 30% lower than that of IEC standard;

4) Reliability: All in-service products have no damages or oil leakage occurred; 

 

 Application:

60 ~220 kV power system of power plant, substation, mining enterprise and etc.

 

Design: relative developed software are adopted in Electromagnetic calculations, strength analysis, leakage magnetic distribution, its electro-dynamic force and electrical insulation.

 

Manufacture:

1)    The core is made of high-permeable grain-orientated top quality cold-rolled silicon sheet and the material is cut with advanced Germany Geoge GmbH automatic shear line with the cut burs controlled within 0.02mm.

2)    The silicon sheet fabrication adopts no-upper yoke lapped technology and all lapped joints of the silicon sheet are 45 full-miters. The laminated  core sheets are integrally pressed and adhered with epoxy resin to make the three leg two-yoke core a strong and flat integral one with good verticality precision, this effectively improves no-load performance and reduces noises.

3)    Bracing plates are used as support between coil leg and inner coil. The iron yoke is tied with epoxy resin-impregnated glass fiber band, and the lower section of oil tank is tightened with counter-pressure bolts.  

1)    The high-voltage (HV) coil adopts an interleaved-continuous structure to improve the voltage characteristics under impact voltage and make voltage evenly distributed. All stays and pads are chamfered to keep highly reliable insulation.

2)    In the transformer winding there is a zigzag oil guide structure so as to fully cool all areas inside the winding, lower the temperature rise of the winding and the hot points of the winding and prolong the service life of insulation. The HV and MV regulation system are independently provided with voltage-regulating winding to balance the ampere turn of each winding,  effectively lower the axial electrodynamic force generated at short-circuit of transformer and improve abrupt short-circuit withstanding capacity.

3)    The winding adopts radial 0 margin designed, between the core and the paper sleeve of LV winding, and between the LV, HV, voltage-regulating windings, as well as before insertion of stays and shroud plate they are fully dried and tightly matched to ensure extremely good compactness and concentricity of the entire winding.

1)  The tank wall adopts wide steel sheet, which will be folded into corrugated structure without splicing, in this way welds are decreased and mechanical strength is enhanced, meanwhile, the corrugated wall has diverging effect, and thus plays a role in decrease of noise. The routing troughs and control cabinets of the secondary circuit are all made of stainless steel, so the entire transformer has a simple and good looking.

2)  All sealing surface use quality sealing material and are precision-machined.

3)  On the edge of the tank there are double sealing grooves, and the outer sealing material is used to shade the atmosphere and ultra-ray to protect the inner sealing being damaged, thus at utmost prolonging service life and enhancing reliability of the seal.

 Main Technical Parameters for 110kV level Three-phase Three-winding OLTC Power Transformer: