Hi,
As stated in Article 250 of NFPA 70, different types of earthing (intrinsically safe, instrument earth(non IS) and protective earth) shall be connected together (apparently) at one point.
But I didn't find any solution to avoid one earth current or voltage, affecting other earthing system in any standard.
If I remember correctly, earth bonding is not a common solution in all countries.
With all that being said, here are my questions which I kindly request your help:
1. How to protect for example intrinsically-safe earth system from protective (safety) earth currents when these two earthing systems are connected together? What's the reference standard and section for the solution provided?
2. If in some other companies, earth bonding is not allowed, what is the reference standard and section?
3. What is pros and cons of each solution?

With many thanks,
Sadeghinia

 

All grounds are connected through their separate grounding connections (field and control system).
Instrument systems use a common ground point but in the field are isolated from local grounding to avoid ground loop currents.

It is not uncommon to find signifficant potetials between separate power grounds in the field, referred to as "ground potentials", that might damage the control room systems.

Intrinsically safe units are electrically isolated from the central control system.

 

All grounds are connected through their separate grounding connections (field and control system).
Instrument systems use a common ground point but in the field are isolated from local grounding to avoid ground loop currents.

It is not uncommon to find signifficant potetials between separate power grounds in the field, referred to as "ground potentials", that might damage the control room systems.

Intrinsically safe units are electrically isolated from the central control system.

Thanks but this is not the answer to any of my questions.
I've stated 3 questions which I need to be answered separately.

 

1. How to protect for example intrinsically-safe earth system from protective (safety) earth currents when these two earthing systems are connected together? What's the reference standard and section for the solution provided?
2. If in some other companies, earth bonding is not allowed, what is the reference standard and section?
3. What is pros and cons of each solution?

For item No. 1, provide the product model number in question. Your supplier advises of specific wiring recomendations and the various standards they meet. Company you are working for can define the standards they adhere to.
For Item No. 2. You've asked a hypothetical question regarding other design practices.
For item No. 3, you'll need to provide specific details of your queries in items No. 1 and No. 2.

 

Can anyone else please check the original message and reply?

 

Unfortunately, it is not an issue that AI can solve in thin air, so specifc details are required

 

This sounds so much like a class assignment that someone is trying to get other people to help with—because AI didn’t produce anything useful.

There are quite a number of useful books and references on grounding (earthing). Whatever earthing method is chosen EVERYONE working on the plant needs to understand and follow the required earthing process. AND, any earthing system(s) need to be properly constructed and tested. And the testing needs to continue long after commissioning is finished.

Earthing is not a “do it this way” system without everyone understanding what “this way” is and how to properly earth different devices. It doesn’t matter what standard is chosen; remember that the best thing about standard is: There are so many to choose from! Literally.

This is reality in the real world. You want answers, not every answer is found in NFPA. There are many other standards in the world, some started simply because of national or regional self-protection reasons. Not every standard is pure and simple.

Your questions are more like statements that you are demanding to be proven or justified. They even lack proper punctuation—and a polite way of asking for help or other references (in addition to NFPA). “One catches more flies with honey than vinegar.”

Refine your AI search question to find the answer you seem to be looking for.

Blessed day, sir.