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Abstract
This report discusses the method of design a grounding system that achieving safety for people and electrical systems, especially in the event of a ground fault. As an introduction, the report studies reasons for the use of grounding systems through comparisons between grounded systems and ungrounded systems stating the reasons which call for the use of grounding systems. In addition, it discussed some methods for grounding electrical systems and how to get the point of neutral of the electrical systems. Different situations that can be taken by human subjected to an electric shock have been studied, and then the equivalent circuit has been analyzed in order to determine the maximum potential that may occur for a human. The different effects resulting from the passage of current in the human body have been studied in order to achieve safe design for the grounding system. As an important part in the design process, the report studied the effects of humidity, temperature, and salt content on the soil resistivity also the methods of measuring soil resistivity. The report discussed, as an important part of the design process, how to calculate the maximum ground fault current could flow in ground grid, and factors influencing it.
as a practical example for all of the above explained, the report discussed steps of designing process for a grounding system for an ac substation.
a computer program written in MATLAP is made to aid substation grounding designer in design process. This program is based on IEEE Standard-80, 2000.
The program allows user to select different types of metals as a conductor material for ground grid also it allows the user to use the standard curves for calculating the fault current division factor. The program also suggests some certain modifications for cases that did not achieve safe design to help user in design process.