Transformer

The design principle of the new type horizontal on-load capacitive tap-changer and the electrical connection and schematic diagram between it and the transformer coil are introduced by the author in this paper.The structural layout and detailed design scheme of the switch are described in detail.The feasibility of the transformer capacity adjustment through the switch is proved by the test waveform of the third party testing institution.

The heating problem of UHV converter station is an important factor affecting the safe and stable operation of the DC transmission system.With the increase of the transmission capacity of the DC project,the types and number of equipment heating failures have increased significantly.Therefore,it is extremely important to analyze the heating problems of various equipment in the converter station.Based on the operation and maintenance experience of the converter station,this paper analyzes the causes of several equipment heating problems and puts forward rectification measures and sug-gestions,which can provide reference for the improvement of the operation and mainte-nance level of UHV converter station and the installation of new engineering equipment.

Cascade current transformer is the use of two or multistage electromagnetic in-duction structure,convert the ultra-high voltage or extra large primary current into a suitable intermediate voltage and current,after two or multistage transformation,the in-termediate voltage and current converted into a low voltage standard current.It is an-other solution to the problems such as the difficulty of wrapping and drying the thick in-sulation of the ultra-high voltage oil-paper capacitor screen insulated current trans-former,and the difficulty of making the synthetic film insulated current transformer with voltage grade of 220kV and above.The design and error calculation method of cascade current transformer are seldom mentioned in the design manual and technical data.In this paper,the working principle of two-cascade electromagnetic current transformer with three secondary windings is analyzed in detail by using principle diagram,equiva-lent circuit and vector diagram.And the error calculation formula is derived.The author also gives a design example and test verification.It is of guiding significance to the de-sign and error calculation of cascade current transformer.

Converter transformer grounding current is higher than power transformer.The source of different structural converter transformer grounding current was analysed.Elec-trical energy method was used to calculate the grounding current and a quick calcula-tion formula was proposed.Contrast calculated value and the measured value,funda-mental wave value are very close.Difference between system and measured harmonic spectrum was analysed.

The temperature rise analysis model of vegetable oil winding with oil duct height from 1mm to 10mm is established. The winding temperature distribution and oil flow velocity distribution under different oil duct heights are studied by simulation calculation. The results show that increasing the oil duct height can effectively improve the winding temperature rise of vegetable oil transformer, but the improvement effect is obvious when the oil duct height is small. When the oil duct height reaches 6mm, the increase of oil duct height does not significantly improve the winding temperature rise. When the oil duct height reaches 8mm, the uniformity of temperature distribution reaches the best.

500kV power grid system has become the main power transmission grid in China.500kV main transformer,high resistance,GIS(HGIS)and other equipment all need to adopt high voltage bushing for electrical connection.Its reliable operation and maintenance determines the safety of power grid equipment.High pressure casing has high seismic vulnerability because of its structural design characteristics.To research the seismic behavior of the high pressure casing,reduce the risk of damage from the earthquake result failure,combining with the earthquake fault case analysis,combing the earthquake cause other problems of the casing failure,this paper analyzes the reason of the casing seismic performance deficiencies are mainly process problems,and through the finite element simulation and 3D seismic shock test verification,A scheme to improve the seismic performance of high pressure casing is put forward for populariza-tion and application.

This paper introduces the first field full voltage long-time no-load test of 500kV large three-phase assembled transformer at high altitude,including the configuration of test equipment and test methods,analyzes the characteristic parameters such as the continuous measurement level of no-load loss,reactive power,voltage and current har-monics and waveform similarity in the process of boosting and continuous boosting,and p.u.ts forward the continuous no-load measurement level and waveform similarity to be included in the diagnosis criteria of no-load test,which provides a reference for carry-ing out long-term no-load test of large-scale transformer at high altitude.

To address the impedance transforming characteristics difference from sec-ondary to primary winding in a co-axial winding transformer between the situations when primary winding is outer winding or is inner winding,a simplified single-phase trans-former model is set,and a series of mathematical derivation analyze the difference be-tween the two situations based on basic principles and uncover the contributing factors.The analysis demonstrates the reason that causes serious inrush current during no-load closing of transformers with inner winding as primary winding,and the reason why much larger current would occur during short circuit tests or short circuit faults in such trans-formers,and thus proves the advantages in inrush current and short circuit current sup-pression of transformers with outer winding as primary winding.

This paper mainly introduces the abnormal noise of a 110kV capacitor voltage transformer in operation of a power supply bureau.It was found that the CVT voltage monitoring data was on the high side,and the cause of the fault was analyzed through diagnostic test and disassembly inspection.According to the test results,it is judged that the reason for the abnormal CVT noise may be that the primary winding of the in-termediate transformer has a short circuit to ground,which makes the tuning function of the compensation reactor ineffective,and the CVT ferromagnetic resonance is excited under certain conditions.The damper has problems in the range and performance of suppressing resonant over-voltage,resulting in continuous abnormal noise.The failure causes were verified through disassembly inspection,providing reference and guidance for subsequent operation and maintenance of the same type of equipment.

Through insulation resistance test,DC resistance test of winding,and combined with lifting core inspection and distribution network lightning positioning system analysis and calculation,a distribution transformer fault caused by lightning induced overvoltage is analyzed,and preventive measures are put forward.

Aimingat three typical insulating materials widely used in converter transformers in operation,measuring the dielectric loss factor under different frequencies and different temperature environments,summarizing the changing law of dielectric loss factor with temperature and frequency,and analyzing the influence of frequency and temperature on the dielectric loss factor of insulation Influence mechanism.The research results show that frequency and temperature have a great influence on the dielectric loss factor of the three insulating materials.Low-frequency and low-temperature dielectric loss factors are small,while temperature and frequency have little influence on them.The medium-frequency and medium-high temperature have large dielectric loss factors.Its impact is big,Therefore,temperature conversion or comparison of dielectric loss data at the same or similar temperature can be used as an effective method to determine the insulation state.

This article briefly introduces the technical characteristics of amorphous alloy closed tridimensional wound-core Transformers,and provides a detailed introduction to the design method and production process of amorphous alloy closed tridimensional wound-core transformers.It also verifies the anti sudden short circuit ability of amor-phous alloy closed tridimensional wound-core transformers from both calculation and ex-periment aspects,indicating that amorphous alloy closed tridimensional wound-core transformers have excellent performance and reliable operation.

This paper introduces the performance difference analysis of n-u and q-u hys-teresis curves of partial discharge of insulating paperboard under typical defects such as moisture characteristics of insulating paperboard from three different manufacturers,and provides feasible suggestions for the selection of insulating materials.The results show that there is no significant difference in Q-u hysteresis curve between the needle-board model and the column-board model.The characteristics of n-u hysteresis curve show that the cylinder-board and needle-board discharges change with voltage,and the discharge times of the needle-board model are much smaller than those of the col-umn-board model.

The FDS of oil-immersed insulation paper and semi-conductive paper with dif-ferent moisture content has been measured.The data measured are fitted as a function of frequency and moisture content using the amendatory Cole-Cole model by means of least square technique.Then the broadband MTL model of the insulation system is es-tablished considering the capacitive electrodes thin layer,and the distribution parameters consider the moisture and frequency dependence.A new method for VFTO distribution calculation of insulation system is proposed.

本文作者分析了 500kV并联电抗器烧损的原因,针对抽能电源系统退运后抽能绕组的改造,提出了 5种方案建议,并对每种方案的优缺点进行了技术经济分析比较,供装有同类型抽能并联电抗器的变电站参考.

1000kV特高压并联电抗器是特高压电网中的核心设备,发生故障时,采用带油带套管整装更换可大幅缩短停电时间,提升特高压电网可靠性.本文对比分析了 3种1000kV特高压并联电抗器更换方式,提出了整装更换14天的标准工期及工艺工序,针对拆装过程中易造成并联电抗器本体油中含气量超标问题,提出并联电抗器整体热油循环24小时工艺,设备更换投运后运行正常,为后续特高压并联电抗器整装更换提供参考.

220kV轴向分裂变压器在进行频率响应测试时,低压绕组经常会出现明显变形甚至严重变形的试验结果.本文作者以某220kV轴向分裂变压器交接时频率响应测试异常为例,通过对频率响应测量试验原理、产品结构以及各种试验的综合分析,对比同类型变压器低压绕组测试结果,明确了低压结构对频率响应测试的影响,发现频率响应分析法对该类型变压器低压侧绕组变形判定不准确,提出了采用电抗法进行分析研究的建议.

本文中作者提出了 一种 自动叠片视觉识别系统,通过调用VISIONPRO中的相关工具完成对硅钢片的重要特征尺寸进行测量,并与标准偏差值进行对比.实际应用效果表明,该方案有效的识别出具有缺陷及精度不能满足要求的硅钢片.

有载分接开关油流保护是变压器主保护之一,其正确动作对变压器的安全可靠运行至关重要.本文介绍了 一起变压器有载分接开关油流继电器误动作导致核电机组停机停堆的案例,对故障原因进行了分析,并提出预防油流继电器、气体继电器误动的改进措施.

采用冷却塔重力自流水冷方式对整流器和整流变进行散热冷却的方式,由于其建造成本低廉、维护运营简单等优点,在产能较低的电解车间应用较为广泛.但在产能提高后,整流器和整流变负荷大幅提升,这种冷却方式已经远远无法满足需求,经常会出现高温报警和轻瓦斯报警,出水温度甚至达到70℃以上.本文作者通过设计与计算,对水冷系统进行升级改造,并将整流器冷却与整流变冷却进行整合;在水循环系统中加入水质旁路软化系统,减少整个水路循环系统中水垢的形成,增加和保持热交换效率;对于循环使用后的废水,增设废水处理池,在经过活性炭对水中悬浮颗粒吸附后,可进入冷却水循环系统,进行重复使用.