Earth Electrode Systems

[AVR_1.0pu]

Hello there,

I was wondering if anyone could help me with my understanding.

If I have a building protected by a lightning protection system with its own electrode, this LPS needs to be bonded back to the Main Earth Bar of the (power) electrical system at a single point.

If this power electrical system consists of say an HV/LV transformer, neutral earthed with its associated (power) earth electrode, what is best practice for the two electrode systems? Can I design a single electrode system that meets both the requirements of lightning protection and power earth (if it were suitably sized, positioned etc)? Do the two systems sit side by side with the soil impedance between them?

I'm assuming combined HV /LV power earth.

Cheers/

AVR

 

[cuky2000]

A common grounding (earthing) system is the most practical way of meeting both the requirements of lightning protection and power earth particularly for building nearby the electrical facility such as a substation.
There is virtually impossible to isolate the two systems since there is a coupling connection through the earth assuming that there are in close proximity.

 

[7anoter4]

For U.S.A NFPA 780 is the recommended practice for lightning protection.
NFPA 780/2011 4.14 Common Grounding.
4.14.1 General. All grounding media and buried metallic conductors that can assist in providing a path for lightning currents in or on a structure shall be interconnected to provide a common ground potential.
4.14.1.1 This interconnection shall include lightning protection, electric service,ommunications, and antenna system grounds, as well as underground metallic piping systems.
In IEC World it is IEC EN 62305 for Lightning Protection.
IEC 62305-4: each conductive service incoming to the structure shall be bonded directly or via suitable SPD at the entrance point.[SPD=Surge Protection Device]

 

[waross]

The first plan is not always possible in the field, but my first plan would be to ground the lightning arrestors by as direct a path as possible.
Then interconnect the other grounding conductors, as near to the grounding electrode as is reasonable.

If your lightning protection is lightning rods then the grounding conductors require special materials (Non-inductive, braided conductor) and routing (No sharp bends, no return bends, always in the direction of the grounding electrode).
The system should be installed as a complete system and then the inter-connections be made.
Care should be taken with the interconnections.
Braided lightning protection conductors are often aluminum.
If rain water passes over copper and then over aluminum it will cause rapid corrosion of the aluminum.
Special methods may be required for the interconnection.

Bill
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