A Three-Dimensional Leader Progression Model For The Lightning Shielding Performance Simulation Of EHV/UHV Transmission Lines

Lightning shielding failure of EHV and UHV transmission lines is one of the mostimportant aspects to cause unscheduled disturbance of the UHV power system. The largescale and high operation voltage increases the probability of lighting strokes to EHV andUHV transmission lines.The traditional lightning shielding analysis models can notcompletely explain the lightning shielding failure mechanism of UHV transmission lines,and support the lightning shielding design. Aimming to develop a new3-dimensional leaderprogression model for lightning shielding performance simulation of EHV and UHVtransmission lines, this paper mainly focuses on the modeling of the self-consistent positiveupward leader and the calculation method of3-dimensional electric field of transmissionlines under thunder cloud and negative downward stepped leader.Firstly, the equivalency of the exsiting positive upward leader test methods by usinglong sparks was discussed. Comparing the electric field spatio-temporal distribution of thedischarge gaps and lightning attachment process, the rod-rod gaps under negative impulsevoltages and the rod-plane gaps under positive impulse voltages can’t reproduce the electricfield spatial distribution during the lightning attachment process. The temporalcharacteristics of the ambient electric field during the lightning attachment process can’t berepresence in the inverted rod-plane gaps under negative impulses. However, the macrofeatures of the positive leader initiated and developed in such typical discharge gaps wereobserved by using CCD high speed cameras, which could provide some fundmental datafor the development and verification of the self-consistent positive upward connectingleader simulation models.Secondly, the calculation method for the streamer space charge produced during thepositive leader propagation was studied here, and a physical model for the positive leaderpropagation simulation was developed on the basis of the thermal ionization theory, whichwas verificated by using the data observed in long air gaps. The influence of the temporalcharacteristics of the ambient electric field on the positive leader propagation in theinverted rod-plane gap was carried out by using this model. A new velocity-current relationduring positive leader propagation was proposed by comparing the simulation results to the recent lightning observation results.Next, the3-dimensional distribution of space electric field in vicinity of thetransmission lines under thunder cloud and negative downward stepped leader wascalculated by using the charge simulation method (CSM). The mesh method andconfiguration of the simulation charge was proposed in the4th chapter. And the parallelcomputation methodology was introduced here to accelerate the solution of chargesimulation equation. The impact of calculation dimensionality, operation voltages andtowers on the space electric field calculation were discussed in the rest of this chapter.At last, by combining the physical model of positive leader propagation and3-dimensional electic field calculation method develop in previous chapters, a new3-dimensional leader progression model for lightning shielding performance simulation ofEHV and UHV transmission lines was proposed, which overcome the disadvantages of theexisting2-dimensional leader progression model. The calculation results of this model werecompared to the operation experiences, which verified the applicability of this model. Thismodel provide a new choice for the lightning shielding performance asseccment of somespecific facilities, such as incoming lines of substation, anchor tower and long span lines.