换流变压器是特高压直流输电系统中的不可或缺的设备之一，其运行可靠性将直

换流变压器是特高压直流输电系统中的不可或缺的设备之一，其运行可靠性将直接影响整个系统的安全可靠运行。运行中的换流变压器除承受交流电压、雷电冲击和操作过电压外，还要承受来自直流、交流与直流叠加及极性反转电压的作用。在这些电压作用下，变压器内部电场分布、绝缘材料击穿特性、空间电荷的积聚与分布等都与普通电力变压器存在很大的差异，并导致换流变压器内部绝缘的异常放电与击穿。因此，对换流变压器绝缘结构进行分析研究是十分必要的。
本文首先阐述了换流变压器的发展状况，介绍了本课题研究的背景、目的和意义。并对主、纵绝缘结构，引线装置和出线装置的国内外研究概况进行了论述。在主绝缘结构设计方面，线圈采用铁心-调压线圈-网线圈-阀线圈的方式，绘制了主绝缘结构计算，运用专业软件VEI对主绝缘结构全域进行交流、直流和极性反转场计算分析，获得电势、场强云图，直观了解主绝缘电场分布，选取特定电位线进行分析，控制和改善油纸交界面的电场强度。在纵绝缘结构设计方面，介绍了波过程原理及等效电路，对各绕组波过程进行验证分析，确定线圈的轴向油道分布、匝间电容补偿结构和端部静电环结构，提高绕组绝缘可靠性和抗短路能力。
在引线装置方面，设计出以一组真空式有载分接开关代替原两组油浸式有载分接开关的调压引线结构，合理选择绝缘距离，优化设计结构，节约了油箱空间。并在实际生产中通过全部型式试验，充分证明所设计结构示可靠的，为今后基于真空开关应用的调压引线结构在特高压换流变压器项目中的广泛应用奠定了坚实基础。
在出线装置方面，采用油纸复合绝缘，重点研究了出线装置中油隙结构的许用场强和固定结构，采用电极覆盖和油隙分隔的方法来改善交、直流电场分布。通过仿真分析，得出电场强度及耐压值，确定绝缘结构是可靠的，从而保证直流出线装置在进行各项绝缘耐受试验时不发生击穿和有害的局部放电。

結果 (英文) 1:

HVDC converter transformers is one of the indispensable device in the system, its reliability will directly affect the safe and reliable operation of the system as a whole. Operation of the converter transformer except under AC voltage, lightning impulse and switching overvoltages, but also comes from the DC, AC and DC superposition voltage and polarity reversal of roles. In the presence of these voltages, breakdown characteristics of electric field distribution in a transformer, insulation materials, space charge accumulation and distribution, there is a big difference with ordinary power transformers and cause abnormal discharge and breakdown of converter transformer insulating. Therefore, the converter transformers is necessary for structural analysis.This paper first describes the development of converter transformer, introduced the background, purpose and significance of the research. And the main, longitudinal insulation structure, lead equipment outlet device and discusses the research at home and abroad. In main insulation structure design aspects, coil used core-adjustable line circle-cable circle-valve coil of way, draws has main insulation structure calculation, using professional software VEI on main insulation structure full domain for Exchange, and DC and polar anti-transitions calculation analysis, get potential, and field images, intuitive understand main insulation farm distribution, selected specific potential line for analysis, control and improved paper junction surface of farm strength. Vertical insulation structure design, introduces the wave principle and equivalent circuits, to validate the windings wave process analysis, determines the axis of the coil to the oil distribution, electrostatic capacitance between compensation structures and end-turn loop structure, improve reliability and ability to withstand short circuit winding insulation.In terms of lead equipment is designed as a set of vacuum type on-load tap-changer instead of the original two sets of oil-immersed surge of on-load tap-changer wire structure, reasonable choice of insulation distances, optimal design of structure, saving space in the tank. And in the actual production of all type tests, fully proved that the structure shown in reliable, for the next surge lead structure based on vacuum switches applied in UHV converter transformer used in a project has laid a solid foundation.In terms of outlet devices, using oil-paper insulation, outlet installations in oil-gap structure focused on strong and fixed structures, using electrodes separated by a gap of coverage and oil to improve AC and DC electric field. Simulation analysis of electric field strength and pressure resistance is obtained to determine insulation structure is reliable, so as to ensure DC outlet devices in carrying out various insulation withstand test without breakdown of partial discharge and harmful.

結果 (英文) 3:

Converter transformer is one of the indispensable equipment in UHV DC transmission system, and its operation reliability will directly affect the safe and reliable operation of the whole system. In addition to withstand AC voltage, lightning impulse and operating over voltage, the converter transformer also bears the function of DC, AC and DC superposition and polarity reversal voltage. In these conditions, all the internal electric field distribution, transformer insulation breakdown characteristics, space charge accumulation and distribution, there is a big difference with the ordinary power transformer, and lead to abnormal discharge and breakdown in the converter transformer internal insulation. Therefore, the converter transformer insulation structure analysis is very necessary.This paper firstly describes the development of the converter transformer, introduces the background, purpose and significance of this research. The domestic and foreign research situation of the main and longitudinal insulation structure, lead device and outlet device is discussed. In the main insulation structure design, the core voltage coil - coil - Cable - ring valve coil, the main insulation structure calculation and drawing, using professional software VEI and AC / DC polarity reversal of the main insulation structure of global field calculation, obtain the potential and the strength of image, intuitive understanding of the main insulation electric field distribution select the specific potential line analysis, field strength control and improve oil interface. In the design of longitudinal insulation, introduces the principle and the equivalent circuit of wave process, analyze and verify the winding wave process, determine the axial oil channel distribution, coil capacitance compensation structure and the end of the static ring structure, improve the reliability and ability of anti short circuit winding insulation.In the wire device, designed by a group of vacuum OLTC instead of the original two groups of oil immersed OLTC voltage lead structure, reasonable insulation distance, structural optimization design, space saving tank. Through all the type test and in the actual production, fully proved that the designed structure shows reliable, widely used for the future application of vacuum switch voltage lead structure in UHV converter transformer based on project has laid a solid foundation.In the terminal device, the insulation, focus on the allowable strength and the fixed structure of outlet device of oil gap structure, to improve the AC and DC electric field distribution by using the method of electrode cover and oil gap separation. Through the simulation analysis, it is concluded that the electric field strength and pressure resistance value, determine the insulation structure is reliable, so as to ensure that the DC outlet device in the insulation resistance test does not occur breakdown and harmful partial discharge.