Research On High-frequency Heating And Drying Equipment And Technology Of Transformer High-voltage Bushing Core

The transformer is an important device to change the AC voltage in the power system and it is an indispensable part to maintain the normal operation of the whole power system.Therefore,the requirements for the reliability and safety of the transformer operation are increasing day by day.Among them,the oil paper capacitive bushing is an important part of the transformer,which is mainly used together with the transformer and reactor.It not only plays the role of supporting the ground and carrying current,but also plays the role of insulation.The normal operation of the transformer is very strict to the operation condition of the transformer bushing,so the technical index requirements of the transformer bushing are also constantly improved.In order to make the transformer bushing reach the insulation state,the core of the transformer bushing must be fully dry.At present,the main drying methods of capacitor type high-voltage bushing core at home and abroad are vacuum drying,oil circulation heating drying,circulation hot air drying and so on.Although these traditional methods have their own advantages and characteristics,they are essentially external heat drying,and there are problems such as uneven internal and external heating,long heating time and so on.In view of the above problems,this paper makes a new research and Exploration on the drying method of the core of the transformer bushing,and adopts the medium heating method to dry the new problem of the transformer bushing,which greatly shortens the drying time on the premise of ensuring the drying quality.In this paper,the failure caused by bushing core and the theory of dielectric polarization are briefly analyzed and introduced.According to the principle of high-frequency medium heating and the characteristics of low boiling point and easy evaporation of vacuum water,a high-voltage bushing core drying equipment is designed,which is mainly composed of vacuum system,high-frequency medium heating system and monitoring and control system.This equipment is the internal heat drying under high-frequency and high-voltage,and is dried in a sealed drying chamber,giving full play to the uniform heating of high-frequency mediumand the vacuum It has the advantages of low boiling point and easy evaporation,and it is equipped with a monitoring and control system based on the real-time monitoring of the multi-point temperature of the high-voltage bushing core and the vacuum degree in the drying room.Taking the drying of 10kV transformer bushing core as the research object,the drying experiment is carried out.When the oscillating power is adjustable from 0 to 30 kW,the oscillating frequency is 6 MHz,the vacuum degree is controlled at 3000 Pa,and the drying temperature is set at 110±3 ?,the drying time can be shortened from 30 days to 72 hours.The dielectric loss factor of the core of the high-voltage bushing is less than or equal to 0.26%,and that of the assembled high-voltage bushing is less than or equal to 0.35%,which meets the process requirements.