Lipeng Liu

On the transition from stable positive glow corona to streamers

A 2D numerical simulation of the transition from stable positive glow corona to streamers in coaxial cylindrical configuration is presented. The hydrodynamic model with several convection-dominated ...

An Efficient Semi-Lagrangian Algorithm for Simulation of Corona Discharges: The Position-State Separation Method

An efficient algorithm without flux correction for the simulation of corona discharges is proposed. The algorithm referred to as the position-state separation (POSS) method is used to solve convection-dominated continuity equations commonly present in corona discharges modeling. The proposed solution method combines an Eulerian scheme for the solution of the convective acceleration, the diffusion and the reaction subproblems, and a Lagrangian scheme for the solution of the linear convection subproblem. Several classical numerical experiments in different dimensions and coordinate systems are conducted to demonstrate the excellent performance of POSS regarding low computational cost, robustness, and high resolution. It is shown that the time complexity of the method when dealing with the convection of charged particles increases linearly with the number of unknowns. For the simulation of corona discharges where local electric fields do not change strongly in time, the time step of POSS could be much larger than the Courant-Friedrichs-Lewy time step. These special features enable POSS to have great potential in the modeling of corona discharges in long interelectrode gaps and for long simulation times.

Two-dimensional simulation on the glow to streamer transition from horizontal conductors

It has been recently suggested that glow corona generated during thunderstorms could have an important role in the initiation of streamers and upward connecting leaders from power transmission lines. In order to further investigate this, a two-dimensional evaluation of the glow corona generation is here reported, which takes into account the non-equilibrium ionization layer around the conductors. The critical change rate of the background electric field required for the transition from glow corona to streamer initiation is obtained. A numerical strategy to evaluate the glow corona to streamers transition for large gaps and irregular geometries is proposed and validated. A four-bundled conductor is also studied and results showed that when evaluating the critical rate of rise of the background electric field for a bundle conductor during thunderstorms, it could be viewed as a single conductor with the equivalent geometric mean radius of the wire configuration. Last, a study case is performed to estimate the effect of the glow corona on the streamer inception from UHV transmission lines during thunderstorms.

Two-dimensional simulation on the glow to streamer transition from lightning rods

In the past twenty years, there has been a growing concern regarding the effect of space charge produced by glow corona on lightning attachment. Several studies have been reported in the literature to evaluate the generation and drift of space charge generated by glow corona from the top of high grounded objects under thunderstorm conditions, using one (1D) or two (2D) dimensional simulations. Unfortunately, the actual transition from glow corona to streamers cannot be numerically evaluated in these studies since the ionization layer was ignored. Thus, a fully 2D detailed evaluation of the glow corona to streamer transition in air is reported, which considers the non-equilibrium ionization layer around a scaled lightning rod. The transition criterion is obtained by changing the applied voltage with different rise rates (dV/dt) after a stable glow corona is formed. The discharge currents as well as the distributions of positive ions, electrons and electric field during the transition of glow corona to streamers are presented. Based on the simulation results, a case study regarding a real lighting rod under thunderstorms is performed. The analysis indicates that streamers can be incepted in the presence of glow corona from both the tip and body of lightning rods under the influence of distant downward stepped leaders.

Application of the Position-State Separation Method to Simulate Streamer Discharges in Arbitrary Geometries

In this paper, we extended the recent work of Liu and Becerra to employ the position-state separation (POSS) method to simulate filamentary streamer discharges. POSS is a semi-Lagrangian method, which solves convection-dominated continuity equations without numerical flux correction. An improved interpolation strategy for POSS is here introduced to overcome the excessive numerical diffusion of the method when very small time step is used. Several benchmark tests in the literature are used to validate the improved method. Numerical experiments show that POSS is an accurate, efficient, and robust numerical method to simulate streamer discharges in arbitrary geometries when combined with finite-element method.