Study On Dielectric Properties And Electric Field Of Graphene Nano-Oil Transformer

In the past few decades,due to the insulating properties of transformer oil,it has been widely used in high-voltage equipment,such as power transformers,high-voltage capacitors,and circuit breakers.It as one of the cores of the power system,often fail.Caused by oil-paper insulation problems.Therefore,the research on the withstand voltage characteristics and electric field of the transformer oil-paper insulation structure is particularly important.In addition,power transformers have the characteristics of complex operating conditions,high insulation levels,difficulty to control operating temperature,and huge footprints.In order to ensure long-term reliable operation of power transformers,while controlling the size and weight as much as possible,better insulating materials are required.This problem of insufficient insulation strength can be solved by adding nanoparticles to the transformer oil for nano-modification.This project is a cooperative project of TBEA Co.,Ltd.Xinjiang Transformer Factory titled Aging Analysis and Experimental Study of Oil-paper Insulation System between Graphene Oil Transformer and Conventional 45# Oil Transformer(Item No.2019-0-43-046).This project carried out the research work on the voltage resistance characteristics and electric field analysis of graphene nano-oil transformers,mainly including the following three parts:(1)A graphene-oil transformer and a conventional 45# oil transformer were selected for aging in a cycle of 7 days and a total of 6 cycles according to IEC 354-1991.At seven time points in the aging process,oil samples were taken from two transformers and power frequency voltage withstand test,DC voltage withstand test and lightning shock voltage withstand test were carried out.In the test process,the difference between different pressure test oil cup electrode and pressure boost mode is considered.The different voltage resistance test results of graphene nano-oil and Karamay 45# transformer oil were obtained.The influence of graphene nano-modification on the voltage resistance of transformer oil was analyzed.(2)Based on the German Novocontrol Alpha?A broadband dielectric impedance spectrometer,the oil samples which were taken at the seven nodes of two transformers were measured by frequency domain dielectric spectrum.The different frequency domain dielectric spectrum test results of graphene nano-oil and Karamay 45# transformer oil were obtained.The influence of graphene nano-modification on the voltage resistance of transformer oil was analyzed.(3)Based on COMSOL finite element simulation software,the oil paper gap insulation structure of power transformer under different aging conditions is modeled by finite element simulation.In the simulation process,the different dielectric characteristics of transformer oil under different aging degree and different temperature conditions are considered.The different electric field distribution results of graphene nano-oil oil paper insulation and Kramay 45#transformer oil paper insulation were obtained.