Distribution Of Corona Space Charge Generated From The UHVDC Overhead Transmission Line During A Thunderstorm

Lightning shielding failure is the main reason affecting the safe operation of UHVDC overhead transmission lines.Under the effect of the DC voltage,the thundercloud electric field and the downward conduction field,a large amount of ions due to corona discharge was generated from the lines and accumulated in the vicinity of the lines to form a corona space charge layer.In order to study the influence of corona space charge on the lightning attachment to UHVDC overhead transmission lines,the distribution of the corona space charge during thunderstorms needs to be studied first.A two-dimensional numerical simulation model was presented to simulate the corona space charge development from DC transmission lines under the effect of the DC operating voltage,the thundercloud background electric field and the electric field produced by download leader.A second-order accurate finite volume method with flux limiter was proposed to solve the ion transport equation,which is the key to solve the corona space charge field.Numerical tests showed that the method effectively reduced calculation errors due to numerical diffusion and numerical oscillation.By using power electronic impact high voltage generator,the experimental study on the characteristics of corona discharge current under the action of dynamic electric field was carried out and the dynamic corona discharge current characteristics of the conductor are analyzed.The shortage that the existing experimental study could only measure the steady-state value of corona current,could not reflect the dynamic corona discharge current change characteristics was covered.The comparison of dynamic current between the simulation and the test was carried out to verify the validity of the time-domain model established in this paper.By using the simulation model,the characteristics of corona space charge distribution of a single conductor during thunderstorm was analyzed,the transition from corona to streamer was studied,the influence of conductor parameters,lightning parameters and environmental parameters on corona space charge distribution and the transition from corona to streamer was acquired.Using the simulation model,corona space charge distribution of a typical ±1100kV UHVDC transmission line during a thunderstorm and the transition from corona to streamer of grounded conductors were calculated and presented.