Study On Full-Time Transient Simulation On Impulse Characteristics Of Grounding System In Substation

Correctly realizing the lightning transient performances of grounding devices isthe foundament of lightning protections of power system and buildings. At present,the developed methods are still difficult to take into account both the time-variant andfrequency-variant characteristics of the grounding girds. The dissertation proposed amethod based on the Hermite primary function, which interpolates in both the timedomain and frequency domain. It can efficiently handle calculating the transientresponses of grounding grids, and get rid of the contradiction between the precisionand the efficiency to some extent.At first, a method called extended unequal potential method is proposed in thisdissertation to obtain correct early time data. It takes into account both the mutualimpedance to ground among grounding conductors and the effect of the ionization inthe soil. The method can be applied with the Bergeron method by transferring thegrounding system into a circuit model.The calculations of the current field in multi-layer soil are difficult. According tothe boundary conditions and the general expressions of Green's Functions,a recursivemethod to obtain the exact expressions of Green's Functions in multi-layer earth ispresented in this dissertation. It avoids the error brought by manual deduction andmakes the calculations of the current field in multi-layer soil more precise.To the purpose of the full-time response, the late time data are also necessary.One dimensional and multi-dimensional two-stage adaptive sampling methods aredesigned in this dissertation. And then, a method based on the union of the traditionalmethod of moments and the intelligent fitting model is proposed in this dissertation. Itcan accelerate the grounding transient calculation by 20 times without any precisionloss.At last, the analysis method of transient full-time response was proposed, whichcan take into account both the time-variant and frequency-variant characteristics ofthe grounding girds simultaneously. According to the particularity of the transientsimulation of grounding systems, a group of preprocesses are constructed for themethod to be applied better in the grounding transient simulation. The experimentalresults verified the precision of the method described in this dissertation.Otherwise, the methods discussed in this dissertation were applied to analyze thetransient characteristics of grounding grids. Detailed conclusions about the transientcharacteristics of grounding systems under versatile lightning waveform, grids size,soil, and current conducting way were drawn.