The oil-immersed power transformer manufactured by Pearl is the latest product designed and developed on the basis of absorbing the most advanced technology at home and abroad. It features high reliability, low partial discharge, low noise, low loss and high anti-short circuit capability. Its excellent and reliable performance have won customers' as well as experts' reorganizations and appreciations.
Low partial discharge: the apparent discharge quantity is usually less than 100pC;
Low noise: Product of 63MVA or below 63MVA has a noise level less than 60dB;
Low loss: no-load loss is reduced by 20 percent compared with that specified in national standards;
High anti-short capability: the SFZ10-40000/110 transformer has passed the short-circuit test carried out by China National Transformer Quality Supervision Testing Center.
The insulation strength is comprehensively calculated with reference to the formula of "impulse voltage gradient+ actuation duration". Parsing imaging method is used for precisely calculating winding magnetic field and ampere-turn balance between windings, thus to minimize the mechanical strength.
Electric field wave process and field intensity are calculated, thus to ensure both the principal and longitudinal insulation having sufficient strength under impulse voltage. Advanced auxiliary computer programs are used to simulate and calculate the temperature rise on core and windings, with precision reaching each core step and each winding disk.
The interleaved and continuous winding structure is adopted for HV windings, thus to improve the electric distribution and effectively improve the anti-lightning impulse capability. Inner and outer support strip structure is adopted. The support strips and pads are all rounded to improve insulation reliability. Oil-directing structure is adopted in the winding, thus to reduce the hotspot temperature and prolong insulation life.
Both the H.V and M.V. windings are usually provided with separate voltage regulating windings, so the ampere-turn of all the windings are completely balanced. These can effectively eliminate the axial electrodynamics force during external short circuit and improve the dynamic stability under external short circuit.
Bell-type tank is adopted for the transformer (for transformer of below-20MVA, barrel-type tank is used). The tank wall is made into a corrugated shape with special machining equipment. This will reduce the welding work and the mechanical strength will be much improved. The tank rims are sealed with oil-resistant rubber pad and there is a position-limit device on bottom part of the tank.
High-quality cold-rolled grain-oriented silicon steel sheets are used for core manufacturing. 45-degree mitring and steps-overlapping structure is adopted. No punching holes in the core. The silicon steel sheet is cut with the most advanced cutting machine, with the cut edging burrs less than 0.02mm. This greatly reduces transformer's no-load loss.
Cooling Devices and Other Accessories:
The main cooling methods for transformers are ONAN (natural air cooling) and ONAF (air forced cooling). Transformers are designed to operate at full load when fans are in operation, and at 70% of the full load when fans are shut down. Panel-type radiators are used. A more compact size can be obtained for transformers equipped with such radiators .The fans generally blow horizontally, with lower speed and lower noise. The on/off operations of the fans are controlled according to changes in oil temperature and load.
Conservator with rubber bladder is used for the transformer, within which are the oil-resistant and sealed bladder for isolating the oil from the atmosphere. To further improve the reliability, the air cell in the bladder are connected with exterior atmosphere through silica gel breather.
GB1094.1, GB1092.2, GB1094.3
GB1094.5, GB/T6451, IEC60076