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Anonymous Poster

Triangular Instrument Grounding

10/31/2010 7:25 AM

For Instrument grounding often separate bars are provided. Those ground bars are then tied to the grounding grid. This is often done with a triangular arrangement with three earth rods that are tied together via copper conductor. One rod is connected to the Instrument ground, one to safety ground etc. The third rod ties to the ground grid and this rod is more deeper that the other two. This system is also called Master Safety ground (MSD).

I want to know the bases of this system meaning which standard is this system following? how do we calculate the grounding electrode size, its depth and distance between electrode etc. Often it is said that it is a vendor recommended system if so that what is the proper grounding method (clean earth) as per standards for instrument and electronics equipment on the plant.

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Guru
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#1

Re: Triangular Instrument Grounding

11/01/2010 5:42 AM

How far down is the water table?

What is the soil condition locally?

In which country is the installation?

What national electrical codes are in force at that place?

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Anonymous Poster
#3
In reply to #1

Re: Triangular Instrument Grounding

11/02/2010 12:39 AM

Water table is at 4 to 4.5 m depth.

Soil resistivity is about 0.85 ohm-m from 2 to 5 meter depth.

Country of installation is Saudi Arab.

BS 7430 and IEEE 80 for area and substation grounding.

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Guru
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#2

Re: Triangular Instrument Grounding

11/01/2010 7:07 AM

See http://instrumentation.web.id/?p=281

It took a while to decipher what you were talking about.
There are no separate earth rods as such. That is if you are referring to intrinsically safe systems.

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