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PowerGMD is designed to compute the substation ground grid. . This is a dialog based interactive program, input data is through interactive dialogs. Features |
Features of Ground Grid Design
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Key definitions: |
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Ground: A conducting connection, whether intentional or accidental, which an electric circuit or equipment is connected to the earth or to some conducting body of the relatively large extent that serves in place of the earth. |
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Grounded: A system, circuit or apparatus referred to is provided with ground for the purposes of establishing a ground return circuit and for maintaining its potential at approximately of the earth. |
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Ground grid: A system of horizontal ground electrodes that consists of a number of interconnected, bare conductors buried in the earth, providing a common ground for electrical devices or metallic structures, usually in one specific location. |
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Ground potential rise: The maximum voltage that a station grounding grid may attain relative to a distant grounding point assumed to be at the potential of the remote earth. |
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Step voltage: The difference in surface potential experienced by a person bridging a distance of 1m with the feet without contacting any other grounded object. |
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Touch voltage: The potential difference between the ground potential rise and the surface potential at the point where a person is standing, while at the same time having hands in contact with a grounding structure. |
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Mesh voltage: The maximum touch voltage to be found within a mesh of a ground grid. |
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Current division factor: A factor representing the inverse of a ratio of the symmetrical fault current to that portion of this current that flows between the grounding grid. |
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In principle, a safe grounding design has two objectives: |
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To provide means to carry electric currents into the earth under normal adversely affecting continuity of service. |
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To assure that a person in the vicinity of the grounded facilities is not exposed to the danger of the critical electric shocks. |
