Analysis And Study On Electrical Insulation And Thermal Characters Of ITER PPEN Transformer

With the rapid development of society and the economy,the challenge of energy shortage becomes more and more prominent,and new energy becomes the inevitable choice of global energy transformation.Fusion energy is a kind of clean(non-nuclear pollution),inexhaustible new energy,the International Thermonuclear-fusion Experimental Reactor(ITER)program is an international scientific project to explore the peaceful use of fusion energy.ITER magnet power supply system includes Pulsed Power Electric Network(PPEN)and Steady-State Electric Network(SSEN)as one of the leading equipment of its transformer is the first barrier to ensure the safe operation of other electrical equipment and the critical equipment to ensure the safety of power grid.The rationality of electromagnetic design,insulation material selection,and insulation structure design of PPEN transformer will be directly related to its operating performance.For this reason,this paper mainly studies the calculation model of the electromagnetic characteristics,insulation characteristics and thermal performance of the PPEN transformer,and proposes the calculation method of its electrical insulation and thermal performance,to ensure that it can meet the voltage tolerance demand of the pulse load and the current and voltage demand of the ITER nuclear fusion device to realize the plasma reaction.According to the load characteristics and operating conditions of PPEN transformer,the electromagnetic calculation model of iron core and winding is established,and the calculation method of no-load loss and load loss of PPEN transformer is derived.Based on the simulation software MagNet,a finite element method was proposed to model and simulate the leakage magnetic field in the PPEN transformer.Based on PPEN transformer main insulation structure characteristics,put forward the finite element method,using the electric field calculation software company to the primary insulation on the modeling and simulation,the distribution of electric field has been the primary insulation of the electric field distribution,according to the results of simulation analysis of the main insulation margin,demonstrates the main insulation design meet the standard requirements.Based on the structural characteristics of the longitudinal insulation of the windings of the PPEN transformer,the paper proposes to reduce the impulse voltage of the windings by placing the capacitor turns in the continuous high-voltage windings with internal shielding.The equivalent circuit model of the longitudinal insulation of the winding is established by using the voltage distribution calculation software bb-xcx001b,and the wave process is calculated and analyzed.Based on ANSYS simulation software,the mathematical and physical model of 2-d steady temperature field-fluid field of PPEN transformer is established.The heat point of winding is calculated in detail by using the Anderson heat point formula,and the heat point temperature rise of winding is obtained.The temperature of the winding hot spot was measured directly by placing an optical fiber probe in the winding hot spot position(predicted value).The temperature field simulation,hot spot calculation data,and fiber optic probe measurement results are compared and analyzed,and the simulation and calculation results are verified.This paper examines the necessity of insulation and temperature rise test of the transformer.According to IEC60076.3:2013 standard and the technical specification of the transformer,the PPEN transformer is subjected to external voltage test,inductive voltage test,partial discharge test,lightning shock test and operational shock test,respectively.The test results show that the whole structure of the PPEN transformer has sufficient insulation strength.According to the requirements of IEC 60076-2-2011 and the technical specification of transformer,the temperature rise test of the PPEN transformer was carried out,and the test results verified that the temperature rise performance of the transformer meets the standard requirements.The research contents and achievements of this paper not only have guiding significance to ensure the safe operation of ITER PPEN transformer to meet the requirements of ITER nuclear fusion device,but also have reference value to the independent design and development of pulse electric network transformer for domestic nuclear fusion reactor in the future.