Research On Frequency Characteristic Of Large Conductor Impedance

The grounding net model is of great importance to the study on conducted interference problem. Calculation and measurement of conductor impedance, which is necessary in determining model parameter and a difficulty as well, is researched carefully in the present paper. Modeling of grounding circuit in power system by adopting the method of PEEC is proposed in the paper, and the result shows that the method of PEEC, by which the frequency characteristics of impedance and voltage drop of interference current between grounding net points are analyzed and calculated, is a valid one. Based on PEEC model of grounding circuit, it was found that the voltage drop generated by impedance and interference current between grounding net points was relevant not only to the structure and material of the grounding net but to the grounding circuit outside the grounding net. There are two distinct effects of the external circuit of grounding net on the parameter, one is that it makes the partial equivalent self inductance change; the other is that the voltage drop between two poles of grounding net is affected by partial mutual inductance. The effect of grounding circuit on the circuit parameter between grounding net points varies with its place. The distribution of current and magnetic field through the metal grounding board with current fed into two terminals is researched in the paper. The result shows that the extent to which the current is infiltrated into the back of the grounding board is correlated with frequency much. The higher the frequency is, the smaller the current density through the back of the metal board. The current distribution through the metal board is affected by characteristics of metal material, and the effect is great. Based on the MTL model of large turbine generator stator windings, the frequency characteristics of their parameters in its slot and the effect of the parameters on transmission characteristics are researched in the paper. The paper includes the research on the frequency characteristics of capacitance parameter of stator windings; the research on the frequency characteristics of their bars in its slot; the effect of frequency characteristics of stator windings'parameters in slot on steep fronted impulse transmission. The frequency characteristics of dielectric constant of stator windings insulation material, the effect of insulation thin layer among strands of stator bar on its capacitance, the effect of iron core laminations space on its capacitance, and the researches on the parameters of stator windings either wrapped in aluminum paper or put in the iron core slot, etc. which are researched by measuring and simulating. And the phenomenon of the steep fronted impulse signals'transmission along stator bar in slot with two speeds is interpreted by the method of simulation calculation.