Earth Grid

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It really depends on the earthing system used in your country but as a general rule earth is earth and if you connect all earths together you will theoretically lower the earth resistance therefore have a better earth all round.

In Australia everything is connected including all equipment and fencing, basically anything metal. It is normal to install an earth grid under the area as well thus improving the earth connection.

In India it is done in a different way.Transformer neutral and DG set neutral should be connected to earth electrodes separately by two independent connections. All protective earthing i.e body earthing should be connected to a common earth grid which in turn should be connected to earth electrodes of sufficient numbers as per calculation. The lightning protection network should also be connected to separate electrodes. All these earthing networks need to be interconnected so as to bring down the effective resistance of the earth grid. However, the interconnections should be at electrode level and not above to ensure direct path of fault current to ground and not through any part of the other earth network.

Dear Mr. Santosh Zingurde,

The answer is NO. Lightnin Arrestor Earting must be independent.

DHAYANANDHAN.S

Please refer to clause no.74 of CEA Regulation 2010 and clause no. 12.3.3 of IS 2309

That is not correct.

Unbonded earthing systems result in step voltages.

You don't want step voltages.

Bond the lot. No daisy chains. You want a star topology.

What does "DG" stand for?

Dear Gurus or Diesel Generator depending on context.

The following items shall have their own independent grounding (earting) in the project.

1. Building grounding
2. Lightning grounding
3. Transformer grounding
4. DG set grounding

Note that grounding and earthing are same terminology, however former is used in USA and latter is used in Europe.

All groundings shall not be connected together at one point. But they inter connect in the following method:

• Transformer grounding is done by the Electrical Supply Company or Utility. They ground the secondary star point of the Transformer winding (Delta/Star connection). This grounding is bonded to neutral( similar to TNC grounding in Europe)
• Building grounding is done by loop bare copper conductor in the ground with grounding rods OR Building grounding is done by 3-eathing rods system
• Building Lightning grounding is done 4-grounding rods connected to 4-down conductors from the Lightning system from roof.
• Emergency Generator (DG Set) grounding is done by 1-earthing rod OR 3-earthing rod system.

Interconnection all independent groundings

1. Building grounding and Lightning grounding is bonded or connected together.
2. Transformer grounded Neutral, Building grounding and Main Distribution Panelboard(MDP) Neutral Bus shall be connected together in MDP. In MDP, Neutral Bus and Equipment grounding Bus are connected together and run parallel for down stream panelboards where they shall be connect to panelboard Neutral Bus and equipment ground Bus respectively but they shall not be connected together in the panelboard as it is done in MDP.
3. DG set grounding Bus, Auto-Transfer switch(ATS) equipment grounding Bus and MDP equipment Bus shall be connected together in ATS only.

If anybody is interested the above earth grid connection diagram of my one of the projects, I will post it.

The main discussion point was interconnection between the various earthing or grounding networks i.e system earthing network ( Transformer or generator), protective earthing network and lightning protection network. You have further elaborated TN-C system on downstream distribution using protective earth and neutral conductor (PEN) as per European Norms.

The transformer neutral point is bifurcated after it is brought out in neutral bushing on transformer tank. One part of neutral conductor goes direct to the earth electrodes through two nos. independent connections, the other part of the neutral conductor is connected to either PEN conductor (in TN-C network), separate N and PE conductor (in TN-S network) or common N and PE conductor at the source which gets separated as earth (E) and neutral (N) bus within the panel (in TN-CS network). In all these systems the neutral is earthed direct and the frames of the electrical apparatus are connected to this point by way of protective conductors (PEN or PE). These networks correspond to multiple-earthed system.

In TT network neutral conductor (N) is connected to earth electrode directly and the frames of the electrical apparatus are connected to earth conductors (PE) which are separate from the system earth (N).

The building earthing network and lightning protection network should be brought down separately and interconnected at the electrode level and not bonded above this point. Otherwise during lightning strike the potential at building earth network may rise to dangerous level.

Yes please. Post the drawings!

Old post, sorry :)

Dear debatao7

Please refer NEC code 250.106 of latest edition(2011) for bonding of lightning grounding rods to Building grounding system

Building grounding system can be 1-rod, 3-rods system, bare copper wire buried around the building or combination of rods and bare copper wire-loop depends on the size of the building.

The same thing what I said in my previously posted comments on bonding of Lightning grounding rods(4No driven in ground) to building grounding system

All earthin Systems within a premises MUST be interconnected.

Dear Electricalexpert65
You are correct that all earthing Systems within a premises MUST be interconnected.However,there is code that tell how to inter connect them. I gave in my previous post procedure of all eathing system inter connections as per NEC code