Some environmental friendly fluorocarbons could be used as substitute for SF

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in power transformers

GIL or even GIS

where they exist as liquid or two-phase flow condition.However

the insulating properties and discharge mechanism of liquid dielectrics under the heated two-phase flow state are not clearly understood yet.We experimentally studied and measured the AC breakdown voltage（BDV） of thermal bubble induced two-phase flow condition of fluorocarbon by self-heating electrodes with different thermodynamic parameters as heat flux

working pressure

and gap distance.According to the results

the BDV changes with heat density like an elongated "Z" shaped curve.And the BDV converting point is highly consistent with the apex value of surface superheat

the eigenvalues and eigenvectors representing the BDV c

onverting point have been proposed accordingly.Finally

a simulation analysis and calculation of insulating and cooling characteristics of a GIL model has been accomplished

which proves the feasibility of the environmental friendly fluorocarbon dielectrics as SF

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substitute used in the new designed GIL.