Earthing system

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ravindraw

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Earthing system used in Sri Lanka is TT. It means supply authority does not provided the earthing conductor through out their distribution. In other way, electricity consumers should be provided the earthing conductor & earth electrode them selves. If we have a system/ device/ machine ( for an example: lift control system ) which was originally designed for TNS, that system whether can be connected/energise to the power supply having with TT. If it is possible to connect to the power supply where the system you get TT, Are we need to make an attention about the earthing....( if specially filters has been used in built in the system.)
 

c-h

Member
Then TN system (the only system allowed by the NEC) requires an effective fault path. It relies on the breaker tripping in case of a fault.

TT relies on a residual current device or ground fault interrupter to switch off power in case of a fault. The earthing (grounding) conductor only leads to a ground rod or water pipe.

The connected machine shouldn't care either way if built to standards. However, filters in the power supply may leak current to the earthing (grounding) conductor. This means the trip current of the residual current device protecting the TT system may need to be set quite high to avoid nuisance trips. (Often devices for this use have ratings in the 100-500 mA range, with 300mA as the international standard)
 
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