Answer / william lobo.

Actually this question should be posted in instrumentation
questions. Nevertheless the answer goes like this. Normal
earthing is connected with the electrical apparatus in the
PIB ( Plant interface building) or any such building
wherein instuments or electronic equipment are installed.
The earthing of these electronic equipment are connected to
a different earthing system which consists of a flat plate
with insulators. From here the earthing goes direct to a
seperate earthing pit and thence the other end of the
earthing pit may then be connected to the ground bus. Never
are any electronic earth connected to the electrical earth
or these electronic sensitive equipment will get damaged.

Answer / kamyar

Dedicated earthing system which is related to sensitive instrument and electronic is known as clean earth system. Althogh for many years engineers by advising standards separate clean earth from dirty (power) earth but nowadays it should be connected togrther at least in one point. The reason is "bonding".

Answer / loboreliance2003

In instrument language the above answer is for the clean
earth system. But the normal electrical earthing system is
termed as dirty earth to which only the housing of the
electronic devices. eg. panels, enclosures,boxes, etc are
connected to the dirty earth.
But the electronic devices etc are earthed to the clean
earth systems only.

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