Simulation Analysis And Experimental Study On Oil Gas Decomposition Process Of Transformer Insulation Under Electric Fault Condition

The transformer is the core main equipment of the power system,and is the key equipment for power transmission and voltage conversion.In order to find the early defects of the transformer,the analysis of dissolved gas in the oil is one of the important means to implement the state maintenance of the power transformer at present.This method reflects the state change of the long-term scale,and the judgment accuracy of the sudden fault defects(breakdown discharge,arc discharge)is insufficient.At the same time,the presence of moisture will seriously affect the distribution ratio of small gas molecules in the insulating oil paper solid-liquid two phases.This can affect the self-diffusion behavior of small molecules,ultimately leading to the accuracy of the DGA’s troubleshooting results.The arc in the breakdown discharge is a high temperature and high conductivity channel.And the energy generated or released by the discharge process is high,a large amount of gas will be generated.Due to the gas production rate is too fast to immediately dissolved in the oil,most of the gas in the form of free gas.A small part gas dissolved in the transformer oil.Therefore,if the law of discharge energy and gas production in time can be grasped,as well as the diffusion mechanism,equipment status information for on-site operation and maintenance personnel can better provided.This is great application value for the safe operation of the power system.In view of the above problems,this paper uses the research methods of simulation combined with experiments,and the main research contents are:(1)Using the molecular simulation method,a mineral oil mixture model containing 20 molecules was constructed according to the composition of mineral oil.The formation path of mineral oil in the same electrical faults,cracking products at different temperatures and small molecules was explored.The number and types of small molecules generated by self-programmed extraction are used to explore the laws between different energies and gas production.(2)The diffusion model of four fault characteristic gas molecules with different water content in the insulating oil was constructed by molecular simulation method.Under the force field of PCFF,the diffusion mechanism of characteristic gas molecules in mineral oil with different water content is studied from four aspects: the diffusion trajectory,diffusion coefficient,free volume and interaction energy of the molecules.This further provides a theoretical basis for the fault diagnosis of transformers.(3)Build a transformer oil gap discharge simulation test monitoring platform,set up two defect discharge models.And use the gradual boost method to conduct oil gap breakdown experiments to explore the law between breakdown discharge energy and gas production.Oil samples with different microwater content are configured to study the breakdown characteristics of mineral oil under different microwater content.