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what is the difference between earthed system and unearthed
system.. where do we use unearthed system because in
electrical catalogues always cable for earthed and unearthed
system is given..pls elaborate
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Answer Posted / s bhattacharya
BASICALLY AS PER LATEST IEC ALL VOLTAGE SYSTEMS WHETHER
400KV OR 415VOLT THE NEUTRAL HAS TO BE GROUNDED AT EACH
LEVEL IN ONE POINT WHETHER SOLID GROUND OR HIGH IMPEDANCE
GROUND.
THE METHOD OF NEUTRAL GROUNDING DEPENDS ON SYSTEM VOLTAGES
1.FOR HV SYSTEMS GREATER THAN 33KV THE NEUTRAL IS GROUNDED
DIRECTLY TO EARTH.
2.FOR VOLTAGES 33KV TO 4kv THE NEUTRAL IS GROUNDED EITHER
THROUGH NGR OR NGT (AS PER THE SYSTEM REQUIREMENT TO LIMIT
THE SYSTEM SHORT CIRCUIT CURRENT IE LIMIT FAULT LEVEL)AND
THIS IS CALLED UNEARTHED SYSTEM.
3.VOLTAGES 415VOLT SYSTEM GENERALLY NEUTRAL IS DIRECTLY
GROUNDED AND THIS IS CALLED EARTHED SYSTEM.
HIGH IMPEDANCE GROUNDING IE FROM 4kv TO 33kV SYSTEMS ARWE
CALLED UNEARTH SYSTEMS AND THIS SYSTEM IS VERY STABLE
COMPARED TO DIRECTLY GROUND SYSTEM.
| Is This Answer Correct ? | 9 Yes | 12 No |
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