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We propose here a cost-effective, realistic method for testing the continuity of the grounding grid and for identifying its weak points or discontinuities. The proposed method involves injecting an ac current of ~200 A frequency not 60 Hz or 60 Hz harmonic into a grounding grid. The purpose of the frequency setting is to be able to distinguish the magnetic field produced by the injected current when...
The ground resistance, the ground potential rise, touches and step voltages are the basic design quantities of the grounding grids. Such quantities greatly depend on the safety of grounding system. The aim being pursued is to minimize these mentioned quantities, while the safety restrictions required by the standard regulations are met. The innovative aspect of the proposed approach is the influences...
A novel topology analysis method is presented to analyze the testability of grounding grids, and creditability is firstly proposed as an important index to evaluate the results. In this method, inaccessible nodes are eliminated by wye-delta transformation, followed by the calculation of testability and creditability index in the reverse direction. Simulation results are provided to prove this method.
With the development of ultra high voltage AC and DC power system, fault current of power plants, substations and convertor station are great than before. Larger grounding grids are needed to meet the safety regulation. Grounding grids usually located in horizon multilayer or vertical multilayer soil structure which parameters such as thickness, resistivity of each layer can be estimated. This paper...
When lightning strikes a substation or a transmission tower near the substation, high current generated by the stroke would flow into the grounding grid of the substation and dissipate in the soil. The transient characteristic of the grounding grid is very important to the safe and reliable operation of the power system. A circuit model with a lumped time-variable parameter is proposed to calculate...
The steel grounding grid buried in earth will corrode and become hidden danger to the safety of power system. It is difficult to get accurate status of corroded ground grid with traditional method. A novel method is presented in order to improve the efficiency and precision of diagnosis. A sine wave exciting current of different power frequency is injected directly into grounding grid by two ground...
A Boundary Element Approach is used to get the numerical computation of grounding system analysis such as the equivalent resistance and the distribution of potential on the earth surface due to fault currents. The results in this paper are produced by the techniques that have been implemented in a computer aided design (CAD) system for grounding grids of electrical substations. The paper investigates...
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