Temperature Characteristics Of Turn-to-Turn Insulation Breakdown Voltage Of Dry-type Air-core Reactor

With the fast development of power system,dry-type air-core reactors have been widely used.However,the burnout failure of dry-type air-core reactors occur frequently in recent years,seriously affecting the safe and stable operation of power grids.The results show that the turn-to-turn insulation failures of dry-type air-core reactors is one of the main causes of the accident,and the influence of temperature on turn-to-turn insulation of dry-type air-core reactor cannot be ignored.Breakdown voltage is one of the most important parameters to characterize the insulation performance,so study on the temperature characteristics of turn-to-turn breakdown voltage of dry-type air-core reactor is very important.In this article,a high-frequency pulse oscillating voltage and power frequency voltage test platform had been set up.Referring to the turn-to-turn insulation manufacturing process of dry-type air-core reactor,aged samples,normal samples and untreated samples were made;The breakdown voltage test was carried out at eight different temperatures,namely-20?,0?,20?,40?,60?,80?,100? and 120?.The breakdown voltage of the samples under different temperature and voltage waveforms was recorded,and their temperature characteristics of breakdown voltage were analyzed.The corona discharge destructive test was performed on the polyester film at the above eight groups of temperatures.The surface of the polyester film was observed by scanning electron microscopy and the surface topography was compared and analyzed.The results show that under a high-frequency pulse oscillating voltage and power frequency voltage,with the increase of temperature,the breakdown voltage of the turn-to-turn insulation of the dry-type air-core reactor will increased at first then decreased in the range of-20? to 120?,it reaches the maximum value when the temperature is 20?.When T<20?,the relation between breakdown voltage and temperature accord with exponential relation,the logarithmic relationship is satisfied when T?20?;the breakdown voltage of normal samples is significantly higher than the aged samples and untreated samples;the breakdown voltage of the three types samples under the high-frequency pulse oscillating voltage is obviously higher than that under the power-frequency voltage;The corona discharge caused holes on the surface of the polyester film.As the temperature increased,the holes first became smaller and then became larger.The holes were the smallest at 20?.The breakdown mechanism of the turn-to-turn insulation was confirmed that the corona discharge first occurred on the insulating surface and it gradually breaks the insulation and eventually causes the insulation breakdown.