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Clean Earth System

Oz
Hi everyone,

I received earthing system design for  the high rise building. Earthing system  single line diagram shows main earthing system and  separate earthing network as clean earth . In every IDF rooms (Telecom Room) there are earth bar and earth bars connected each other for every floors every IDF rooms and its connected in the end to the  main clean earth bar in the main telecom room and main clean earth bar connected to the separate earth pits with earth electrodes. There are main earthing system as well but there is no connection between the main earthing system and clean earth. Earth pits ,earth electrodes,earth bars are all separate .The thing is telecommunication rack fed by the industrial socket inside the IDF Room  and this sockets fed by UDB(UPS DB) in electrical room. UDB connected to the main earthing system within the earth bar inside the electrical room .Telecommunication rack cabinet body connected to the clean earth bar inside the IDF room. So after all separations between main earth and clean earth , they are connected through rack cabinet bonding. My question is what is the purpose  of the "clean earth " provided in this design . And what I tried to explain above is correct practice?
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    It is sometimes done to create separate circuits to form segregated "clean" and "dirty" supplies to things that need protection, and possible sources of interference respectively  As part of that the earthing may be split as near to the supply origin as possible.

    Even so, for ADS to work safely and well, there should always be some connection between the clean and dirty earths, though that connection  may be arranged to be a very low impedance at 50 Hz and still a significant impedance to fast pulses / high frequencies. This may take the form of a ferrite cored inductor or just a long route, usually via the main earth terminal.

    Such systems need sympathetic maintenance with understanding, as it is all to easy to defeat the intention by accidentally cross coupling the clean and dirty sides in the mistaken belief that it will improve things.


    More generally segregated systems are often a sign of troubles in the face of EMC issues, and it is generally  preferable to fit suppression and filtering local  to the 'dirty' equipment if at all possible, so the whole system is just "clean" and then there can be a single low impedance ground plane
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    It is sometimes done to create separate circuits to form segregated "clean" and "dirty" supplies to things that need protection, and possible sources of interference respectively  As part of that the earthing may be split as near to the supply origin as possible.

    Even so, for ADS to work safely and well, there should always be some connection between the clean and dirty earths, though that connection  may be arranged to be a very low impedance at 50 Hz and still a significant impedance to fast pulses / high frequencies. This may take the form of a ferrite cored inductor or just a long route, usually via the main earth terminal.

    Such systems need sympathetic maintenance with understanding, as it is all to easy to defeat the intention by accidentally cross coupling the clean and dirty sides in the mistaken belief that it will improve things.


    More generally segregated systems are often a sign of troubles in the face of EMC issues, and it is generally  preferable to fit suppression and filtering local  to the 'dirty' equipment if at all possible, so the whole system is just "clean" and then there can be a single low impedance ground plane
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