Research Of Wave Process And Winding Model In UHV Power Transformer

The UHV power transformer is the key equipment of UHV smart grid,which characterized by high voltage and large load capacity.In the operation of the system,it is easy to be affected by various internal and external overvoltage,especially the lightning impulse overvoltage,which is more important to the transformer's main and longitudinal insulation structure.Due to the high voltage level of the product and the limitation of the transportation conditions,it is impossible to increase the size of the transformer,the insulation distance and the insulation thickness.Therefore,in the design of UHV Transformer,firstly,we should solve the longitudinal insulation structure rationality and reliability problems,and under the premise of reliable quality,ensure product safety and operation reliability.In this paper,the research status of longitudinal insulation structure and strength of power transformer is analyzed by referring to the relevant literature.Firstly,under the lightning impulse voltage,the calculation of capacitance and inductance parameters of the equivalent circuit of the transformer winding is studied in detail.Then,combined with the practical engineering experience,the capacitance compensation effect of a variety of winding structure is analyzed,and taking the typical UHV 1000kV auto transformer as an example,designing the structure of high voltage winding,medium voltage winding,low voltage winding,regulating winding and compensating winding.Finally,the lightning impulse voltage of the winding is calculated and analyzed by using the software of lightning impulse voltage,and the types of all kinds of coil are determined.In order to verify the differences between the theoretical analysis and the actual situation of the lightning impulse,the impulse voltage test and method of the actual winding model are studied.Firstly,the principle and characteristics of several coil model tests are studied.Then,according to the deficiency of the previous test methods,a new measuring method of coil voltage under lightning impulse is presented.The scale model is studied,and the model is tested with low voltage.The simulation results and the measured voltage distribution are compared.Finally,the lightning impulse test method of high voltage is studied,and the lightning impulse test is carried out to evaluate the insulation strength of the coil structure.The analysis showing that there is no breakdown and discharge phenomenon in the winding structure,winch laid a solid foundation for the product design of UHV Transformer through the high voltage test.