Compared with mineral oil, the eco-friendly ester group insulating oil not only possesses good electrical performances but also owns great biodegradability and high flash point. Therefore, it is very necessary to carry out the simulation of streamer discharge in ester group insulating oil. However, all the existing simulation models have the disadvantage of overestimating the electron speed. According to the existing literature, the electron speed may reach its saturation speed under an extremely high electric field. Therefore, this paper will introduce the electron saturation velocity for modeling and simulation. In this paper, A simulation model is established by using the 2D-axisymmetric dimension in COMSOL Multiphysics 5.6 software. The motion characteristics of charged particles in the liquid dielectric discharge process are described by Poisson equation and three current continuity equations. The simulation model uses the coupling of the current continuity equation and the electric field Poisson equation to calculate the distribution of charged particles during streamer discharge. Model of electron velocity (derived from density functions) as a function of electric field intensity. Through simulation analysis, it is found that the simulation model of streamer discharge considering the electron saturation velocity has a very similar streamer propagation velocity to the experimental results. The electron velocity described by ESV model is limited at intense electric fields. Therefore, electrons are no longer capable of keeping the volume within the streamer column almost electrically neutral and as a consequence the electric field intensity increases within the streamer column near the needle electrode and secondary ionization occurs. Finding of this paper explains regime of positive streamer propagation velocity using a nonlinear electric field dependent electron velocity model that describes the streamer velocity more accurately compared to the experimental result in the literature.

ester group insulating oil，streamer, electron saturation velocity, streamer propagation velocity, modelling