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.
