Research On The Eddy Current Loss And Temperature Field Distribution Of The Dry-type Iron Core Reactor Winding

The reactor,as it can effectively limit the short circuit current in the power transmission system and compensate the reactive capacity,has become an important auxiliary equipment in the long-distance transmission.Compared with the oil-immersed core reactor,the dry-type core reactor has the advantages of small volume,convenient installation,long service life and no electromagnetic pollution.It has been widely used in urban power grid.With the increase of reactor operating capacity and the influence of its own structure and external environment,the problem of local overheating becomes more and more prominent.Overheating of the reactor windings not only accelerate s the aging of insulation material and affect s the life,but may even lead to serious consequences of partia l burning.Therefore,researching the winding eddy current loss and temperature field distribution of the dry-type core reactor ha ve important significance for the design of the reactor,real-time online monitoring and fault prevention system in the enviro nment of the Internet of things.Based on the basic principle of electromagneti sm,a certain type of three-phase dry-type core reactor is taken as the research object.Two-dimensional and three-dimensional simulation models are established respectively acc ording to its structural characteristics.Firstly,the distribution of leakage magnetic field of the reactor is analyzed in Maxwell.Based on this,the eddy current loss distribution and loss values in the winding are further calculated.Then the magnetic and thermal coupling calculation methods of Maxwell and Fluent are used to get the temperature field distribution,hot spot location and temperature rise of the reactor winding.The main contents of this paper are as follows:(1)According to the basic laws of Maxwell’s equations,the partial differential equations of the magnetic vector are deduced,and the magnetic field characteristics of the dry-type core reactor are used to describe the three-dimensional mathematical model of the electromagnetic field of the reactor through mathematical expressions.On this basis,the two-dimensional electromagnetic field of the reactor is solved by the finite element method,and the distribution of the magnetic field lines of the reactor is basically in the form of upper and lower symmetry,among which the bending of the magnetic lines at the upper and lower ends of the winding is the most obvious.(2)A three-dimensional finite element model was established based on the structural characteristics of the dry-type core reactor.The distribution of the main and leakage flux of the reactor was calculated by using the Maxwell’s three-dimensional electromagnetic field analy sis module,and the analysis of the axial magnetic flux leakage component and the radial leakage magnetic flux component of the phase A winding at the time ωt=0 is performed.The maximum axial magnetic flux leakage component is 42.23 m T,which is located in the position where the innermost winding is parallel to the air gap of the core column 2/3 height.The maximum value of the radial leakage magnetic flux component is 29.14 m T,located at the top of the innermost winding upper end.(3)Based on the analysis of the distribution of leakage magnetic field,the effect of eddy current on the winding current density is discussed,and the distribution law of eddy current loss is summarized.The eddy current loss at the upper and lower ends of the winding is the lar gest,followed by the outer part of the core at the height of the air gap;the eddy current loss in the winding is 11.7W calculated by the finite element method,which accounts for 5.3% of the total winding loss.(4)The magnetic and thermal coupling calcu lations of Maxwell and Fluent were used,combined with the principles of heat transfer and fluid mechanics to analyze the process of heat generation and heat dissipation of reactors.A three-dimensional model of the reactor’s temperature field and fluid fi eld is established,and the temperature field distribution of the reactor winding is calculated in the solution domain through the Fluent flow and solid coupling module.The hottest spot is located at 90% of the axial height of the second layer inside the center phase winding,and the temperature rise reaches 124 K.