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Transcript
GROUNDING Presented by: Mohammed Amerah Mohammed Horiah The Definition of Grounding • In electrical engineering , ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth. • electrical power distribution systems, a protective ground conductor is an essential part of the safety Earthing system. Why we use Grounding: 1- EARTH Wiring is distribution line • Look at this picture There is a wire on the top of distribution line. • This is called earth wire or ground wire • Why we use this wire ? • The main job for this wire is to save the distribution wire from Detonators • How much the current and voltage for these Detonators? • It is 25kA and very high voltage • How can the Earthing wire suffer this value ? Why we use Grounding: 2- Connections to ground limit the build-up of static electricity • In some telegraph and power transmission circuits, the earth itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor. • For measurement purposes : • the Earth serves as a (reasonably) constant potential reference against which other potentials can be measured •An electrical ground system should have an appropriate current-carrying capability to serve as an adequate zerovoltage reference level. • In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential. Grounding issues: 1- A real ground connection has a significant resistance, the approximation of zero potential is no longer valid. 2- Extra cost 3- Work as return path to the sources or transformers. The Difference between ground and neutral • Ground wire has zero potential . • Buried in ground. • Neutral wire is The secondary wire which closes the circuit. • All neutral wires are connected to ground wire. Convert Ungrounded to ResistanceGrounded Systems