Earth Pits Interconnection

M

Muzammil.qazi

Member
Location
Karachi
Occupation
Electrical Design Engineer
In our project we have meshed/interconnected several earth pits together (inter-pit bonding / meshing). The execution team used 16 mm² copper cable upon my suggestion, as I heared from some where for the bonding conductor. Now the client while executing asking basis of this selection, he insists that such interconnection should use much larger conductor (for example 95 mm² copper). I am new with 1 year experience only, and completely disturbed how to tackle him. Pls help.


My questions:
  1. Does any internationally recognized standard (e.g. BS 7430, IEC 62305‑3, or any other) explicitly mandate a fixed conductor cross-section (e.g. 25, 50, 95 mm²) when meshing or bonding earth-pits ?
  2. If there is no such fixed-size clause, what is the correct standard-based method to select the conductor size for earth-pit interconnection ?
  3. How does adiabatic equation helps in this ?
 
What kind of system are you earthing ?
Most of us here are not familiar with the British standards, 16 mm² is about the same as our 6AWG and that is the maximum size required for bonding two ground rods here on our TN-C-S system.
I imagine there are too many details for us to be much help as we don't use the British standards here and we definitely don't use TT systems which I am guessing you have.
I would try a UK electrical forum.
You can find 7430 here:
 
Most of the discussions here center around the US National Electrical Code and the related Canadian codes, there is some knowledge of international standards but it's not the emphasis.

Assuming that "earth pit" is a dug pit with an earthing/grounding electrode suggests the IEEE green/emerald books would be a good starting point (the US NEC would generally not require such pits or meshing)-

IEEE Recommended Practice for System Grounding of Industrial and Commercial Power Systems

Questions like these are easier to answer with context - for instance, does this involve a commercial building, an antenna tower/structure, a power generation plant, or that? What local codes apply?
 
So it looks like the electrical code there is based off of older NEC

Pakistan uses its own national codes, primarily the Pakistan Electric and Telecommunication Safety Code (PETSAC-2014), which is based on the U.S. National Electrical Safety Code (NESC). For building installations, the Building Code of Pakistan (including seismic and fire safety provisions) also contains relevant electrical requirements. Additionally, some standards, such as the 18th Edition of the IET Wiring Regulations (BS 7671), are adopted for new electrical installations, and specific sections of NFPA or ANSI/NETA standards may apply depending on the project.
Click to expand...
 
Thankyou for these questions, Actually here in Pakistan we mostly follow IEC standards, but when things are easier to explain with reference to other standard like in my case BS 7671 was somehow supporting me, we dont hesitate to use .

Comming back to main question, This is a Power house of a Industry, with their captive power including BESS Containers , Skids , Trafo’s, MV Panels. Lightining Arresters, all are connected with different Pits , but at the end, In design we have interconnected all pits throuth 16 sq.mm cable, as my manager told me that we will create a mesh of all earthing pits used.

All other grounding cable sizes I calculated using adiabatic equation for cable sizing.
tortuga said:
What kind of system are you earthing ?
Most of us here are not familiar with the British standards, 16 mm² is about the same as our 6AWG and that is the maximum size required for bonding two ground rods here on our TN-C-S system.
I imagine there are too many details for us to be much help as we don't use the British standards here and we definitely don't use TT systems which I am guessing you have.
I would try a UK electrical forum.
You can find 7430 here:
Click to expand...

tortuga said:
What kind of system are you earthing ?
Most of us here are not familiar with the British standards, 16 mm² is about the same as our 6AWG and that is the maximum size required for bonding two ground rods here on our TN-C-S system.
I imagine there are too many details for us to be much help as we don't use the British standards here and we definitely don't use TT systems which I am guessing you have.
I would try a UK electrical forum.
You can find 7430 here:
Click to expand...
 
zbang said:
Most of the discussions here center around the US National Electrical Code and the related Canadian codes, there is some knowledge of international standards but it's not the emphasis.

Assuming that "earth pit" is a dug pit with an earthing/grounding electrode suggests the IEEE green/emerald books would be a good starting point (the US NEC would generally not require such pits or meshing)-

IEEE Recommended Practice for System Grounding of Industrial and Commercial Power Systems

Questions like these are easier to answer with context - for instance, does this involve a commercial building, an antenna tower/structure, a power generation plant, or that? What local codes apply?
Click to expand...
Thankyou for these questions, Actually here in Pakistan we mostly follow IEC standards, but when things are easier to explain with reference to other standard like in my case BS 7671 was somehow supporting me, we dont hesitate to use .

Comming back to main question, This is a Power house of a Industry, with their captive power including BESS Containers , Skids , Trafo’s, MV Panels. Lightining Arresters, all are connected with different Pits , but at the end, In design we have interconnected all pits throuth 16 sq.mm cable, as my manager told me that we will create a mesh of all earthing pits used.

All other grounding cable sizes I calculated using adiabatic equation for cable sizing.
 
Muzammil.qazi said:
Comming back to main question, This is a Power house of a Industry, with their captive power including BESS Containers , Skids , Trafo’s, MV Panels. Lightining Arresters, all are connected with different Pits
Click to expand...
I believe your discussing what we call a 'substation' and substation grounding'
 
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