Magnetic Interference Shielding And Optimization Design Of Dry-type Air-core Reactor

Dry-type air-core shunt reactor is an important reactive power compensation device in the power system,and the stability of its operation is directly related to the quality of the power transmission in the power system.The electromotive force generated during the operation of the reactor may cause the cracking of the encapsulation insulation,which in turn causes damage to the reactor.There are two main reasons for the insulation cracking: excessive electromotive force generated by the leakage flux causes strength damage;leakage;The magnetic flux generates alternating electric power and causes fatigue damage.In the engineering,only the tensile strength limit of insulating materials is specified,and the fatigue damage research is not enough.This article uses Maxwell magnetic field simulation software to analyze the magnetic field distribution of dry-type air-core reactors,and verifies that during normal operation,even if the electromotive force generated by magnetic flux leakage meets the tensile strength requirements of the material,it does not meet the strain margin for fatigue failure.Therefore,magnetic leakage shielding is necessary.The specific work of this paper is as follows:(1)Calculate the magnetic field distribution of dry-type air-core reactor according to Biot Savart’s law and superposition principle,use Maxwell magnetic field simulation software to establish a single-phase dry-type air-core reactor finite element simulation model,and obtain the magnetic field value of the air-core reactor through magnetic field simulation Distribution value.According to the electrodynamic formula,the winding encapsulation tensile strength is calculated.The results show that,according to the engineering requirements,on the basis of meeting the space distance requirements,the insulation tensile strength meets the design requirements,but the fatigue stress design margin is small,especially for long-term operation of insulation In the case of aging,the risk of insulation damage is increased.(2)In order to reduce the damage of alternating magnetic flux leakage and electromagnetic force to the insulation encapsulation,according to the principle of high magnetic permeability shielding,this paper proposes a new magnetic leakage shielding method,which is equipped with high magnetic flux inside the air core reactor.Conductivity shielding structure to reduce the influence of magnetic leakage.The simulation results show that the shielding effect is the best when the shielding structure is located at 1/2 of the height of the reactor,and the magnetic leakage is reduced by63%;in order not to affect the normal operation of the reactor,the maximum radius of the shielding structure at 455 mm,magnetic leakage is reduced by 80%;the thickness of the shield has little effect on magnetic leakage.(3)Apply the shielding structure to the three-phase reactor group to reduce the magnetic leakage and reduce the distance between the reactor phases to 1.4D.Reducing magnetic flux leakage can effectively reduce eddy current loss and temperature rise.In this paper,a star-shaped frame eddy current field simulation is carried out.After shielding is installed,the magnetic field can be reduced from 90 m T to 45 m T,which can prevent and alleviate insulation aging to a certain extent.