Best Grounding Design for an Office Building

[arvinolga]

Hi,

Anyone who can comment on the best practice regarding grounding design of an office building. Some info on the system:

Transformer: delta-wye
System voltage: 400/230V

Also, the building will have a lightning protection system. Should the lightning protection's grounding system be separate from the building grounding system?

Thanks
Arvin

 

[rbulsara]

arvinolga:

1. This is a very general question. For starter you need to review applicable electrical codes in the area you are located. Where are you/your project located?


2. In absence of other codes, follwing NEC (NFPA 70 publichsed by NFPA) would be the best course. You need to read up on that. Also IEEE Green book.

3. Most common in the USA is to connect the service transformer neutral to the water service pipe on the inlet side plus connect to the building steel. There are many other options.

4. Lightning protection system must be bonded to the building service grounding electrode system. It cannot be separate from it.

 

[arvinolga]

Thanks. This is a Philippine project.The neutral portion of the system will also be bonded to the building service grounding system, right?

So this means that the service transformer neutral and lightning protection sytem must be bonded together with the building grounding system?

 

[rbulsara]

In general yes and yes.

The neutral of the service transformer should only be grounded at only one point, that is at the service disconnect.

You really need to consult local experienced engineer and read up the books I suggested. This forum is no substitute for talking to someone in person.

 

[arvinolga]

will do, thanks!

 

[DrDrreeeaaa]

It depends on your earthing system.

In Australia (TN-C-S) the transformer star point is earthed and the main switchboard is earthed. The MSB also contains a main earth-neutral link. The earth electrodes are designed to meet code guidelines. There may be some earthing of water pipe/building steel throughout the building and our standards have recently made this more onoerous after someone was electrocuted by an insulation fault in the basement of an apartment building that energised bathroom building steel on the 40th floor.

As for the lightning protection I would say it should be earthed since the idea is to make sure the lightning protection conductors are at a lower potential than the building conductors. I could be wrong about this though...

 

[arvinolga]

Thanks. The question now really is whether to bond the three together or just to separate the lightning protection with its own grounding system.

 

[jghrist]

The lightning protection should have a separate grounding electrode system, but should be bonded to the power ground at a single point.

 

[NCTHAI]

It is opined that .....

- Power supply Ground (Neutral) should be grounded at only one point.

- Power supply ground (Neutral) and Protection Ground (Body grounding of Transformers, motors or other equipments, including lightning protection) should be separate.

- Multiple connections for protection ground are accepted (in fact desired)

- At the end of the it is single ground.

NC