Study On Aging And Evaluation Technology Of Dry-type Air-core Reactor

With the use of dry-type air reactor in the power grid,due to the limitations of the manufacturing process,the high-frequency overvoltage produced during the cutting and the long running time under the bad working conditions,the faults often occur and cause huge economic losses.Sufficient evidence indicates that a large part of the accident was caused by the failure of its turn insulation.Therefore,it is of great significance to study the aging characteristics of the inter-turn insulation of dry-type air reactor and its insulation diagnosis technology to ensure its safe and stable operation.The overvoltage caused by the operation of dry-type air-core reactor is one of the main factors causing the turn-turn insulation damage.Based on the main wiring of a substation,the equivalent circuit is constructed,and the influence of the switching overvoltage and the different parameters on the different current state is analyzed.It can be seen from the analysis that with the increase of switching current,over voltage increases,in the 40 A current state,the overvoltage coefficient is up to 40 times times,the overvoltage is also affected by the ground stray capacitance,equivalent inductance and other parameters.In order to understand the effect of overvoltage on the turn insulation aging of the reactor,according to the turn insulation structure of the dry-type hollow reactor,turn the insulation sample,and set up a single thermal aging test platform,alternating voltage withstand test platform,Pulse oscillating overvoltage test platform.The thermal aging,electric-thermal combined aging under power-frequency voltage,and electric-thermal combined aging under impulse voltage are analyzed by analyzing the test data:Dry-type hollow reactor turn insulation in a single thermal aging effect,its aging degree is basicallyunchanged,in more than 25 years,the test specimen pressure level to appear a significant downward trend,in the equivalent operating life of 30 years,its insulation level decreased by 30.5%,It is indicated that pure thermal aging is not the main reason for the aging of the turn insulation of dry-type hollow reactors.However,under the power-frequency voltage of electric-thermal combined with aging,shock voltage under the electric-thermal combined aging,the speed of insulation aging is significantly faster.Under the action of power frequency 2kV electric-thermal combined aging cycle,the insulation level decreased by 39.37%,and the insulation level decreased nearly 40% under814,433 times of 2kV impulse voltage-heat combined with one cycle.This shows that the dry-type air reactor in the cut-output overvoltage is one of the main factors affecting the insulation level between the turn of the core.In order to diagnose the turn insulation fault,the inductance quantity in the process of turn insulation fault is analyzed by the magnetic vector method,and the inductance quantity decreases with the increase of the fault component and the same fault,and decreases with the fault position moving toward the center.On this basis,combined with the recommended test method of turn over voltage in the GB1094.6-2011 standard,and on the basis of its parameter analysis,the paper designs the inter-turn insulation diagnosis system which is suitable for field test,and carries on the simulation and the field test.It can be seen from the test results that by comparing the test waveforms under low voltage and full voltage during the test,when the waveform over 0 points coincide with the different test voltages,the inductance of the reactor is not changed in the test process,and its insulation is good.When the waveform over0 points does not coincide at different test voltages,the test waveform at high voltage is higher than the waveform under low voltage,then it shows that the insulation between the turns is good fault.It can be seen from this test that the diagnosis of turn insulation of dry-type hollow reactor is realized by analyzing the test waveform under different voltages.