| After more than 40 years of development,China’s northwest power grid has formed a large regional power grid with 330kV power grid as the backbone,featuring coordinated development of power grids at all levels,more stable power transmission and a reasonable structure.In Shaanxi,Gansu,Qinghai and Ningxia provinces(regions)where the electrical load is concentrated,330kV power grid is generally used,and it covers and extends throughout northwest China,becoming the principal power grid of main power supply.With the large-scale construction of high-speed railway lines In northwest China during the“13th Five-Year Plan" period,it is an irresistible trend to develop 330kV VX-connected single-phase three-winding traction transformers that conform to the characteristics of the northwest power grid.However,330kV traction transformers are traction transformers with the highest voltage grade in China,thus there is no ready-made experience for reference for our company in terms of design.In this paper,the design work is carried out according to the technical requirements of 330kV VX-connected single-phase three-winding traction transformers.Firstly,determine core structure and material trademark,calculate the diameter of core and the potential of each turn of winding,complete design for the axial height and radial size of winding,and determine the structure of winding.Secondly,design the main and longitudinal insulation structure of transformer according to the voltage grade,determine insulation distance,calculate short-circuit impedance and no-load and load losses,and calculate temperature rise according to loss value.Finally,calculate electrodynamic force and wire stress according to the sudden short-circuit condition to ensure the safety and reliability of transformer.Two schemes are designed in this paper.According to Scheme 1,the voltage regulating range is 330 nge re and no voltage regulating winding is set.According to Scheme 2,the voltage regulating range is 330±4xis 3 and a voltage regulating winding is set.The two schemes are compared and analyzed after completion of design:Scheme 1 is superior to Scheme 2 in respects of no-load loss,load loss,short-circuit impedance and winding temperature rise,while Scheme 2 is superior to Scheme 1 in respects of no-load current,insulation structure,voltage regulation range,winding stress,short-circuit mechanical force and cost.By comparing and analyzing the two schemes,Scheme 2 is determined as the final scheme.A prototype is produced according to the final scheme,and the design parameters of the final scheme are verified by the test data of the prototype.The verification results show that the scheme is of good technology,high reliability and low loss and fully meets the technical requirements. |
