Study On Electrical Characteristics Of Grounding Systems

As one of the most widely used measures for electrical safety, grounding is essential for the normal operation and fault protection of all kinds of electrical and electronic equipment. It is also indispensable for ensuring the personal safety in power systems. In recent years, the development of electric power systems leads to a continuous expand of the grid scale and a growth of short circuit currents, which imposes a stringent requirement on grounding design. In the grounding design, a great deal of attention has been paid to the electrical characteristics of grounding systems. The purpose of this article is to study and analyze the electrical characteristics of grounding systems. The research project is completed in three aspects, i.e. calculation of grounding resistance of grounding grid in heterogeneous soil; calculation of grounding resistance of grounding grid in non-homogeneous soil; and study on impact characteristics of grounding system.Calculation of grounding resistance of grounding grid in heterogeneous soil is first made by the average potential method.The algorithm is proposed and programmed in MATLAB. A comparison is made between calculated measured values of grounding resistances to verify the validity of the proposed algorithm. By means of the computer program, the influence factors are enquired for grounding resistances, which can provide a sound basis for grounding design of power system.Following the analysis and calculation of grounding resistance in heterogeneous soil, the further algorithm is proposed for non-heterogeneous soil. In consideration of the limitation of the previous methods for calculating the grounding resistance in heterogeneous soil, a calculating model is built to determine the grounding resistance in two-layer soil by using the average potential method and image method. Then, the program is developed in MATLAB by using the model and algorithm. and a verification is made for the accuracy of the algorithm through numerical examples, The investigations are also carried out into the influence of buried depth, soil resistivity and soil thickness on grounding resistance in non-heterogeneous soil.Under the case of injecting lightning impulse currents, the transient behavior is investigated on the grounding systems. For calculating the transient responses of grounding systems, the distribution parameters effect of grounding device and ionization effect of soil have been detailed instructions, and a simulation model is built in the software. The simulated results are compared with the experimental results and a reasonable agreement appears between them, which confirms the validity of the simulation model. Afterward the influence factors such as current amplitude, configuration size, soil resistivity are inspected on impulse grounding resistance, which will contribute to the design of grounding system.