Ground bonding to existing ground grid 1

[sparkview]

Hi all,

We are currently building a Flywheel system of about 5 MW which is planned to be connected on an existing power plant switch-gear (12.6 kV). This switch-gear also feeds other auxilary sections of the power plant.
The new installation will be equipped with a new ground grid and includes earthing rods. Should the new ground grid installation be also connected to the existing ground grid and why? Is there any standards that support this matter?

Any help is highly appreciated.

Kind regards,

Jairo

 

[farale]

Based on new IEC publications, it is necessary to have all earthing systems connected to each other.
A simple reason is: different points of the earth may have different potentials in short circuit or lightning conditions. If earthing systems are isolated, then exposed conductors or enclosures may have different voltages, which is dangerous if someone touches two enclosures at the same time.

You were allowed to have isolated earthing systems in a single plant as per old VDE codes, but I believe the codes are no longer applicable.

 

[sparkview]

Hi farale,

Thanks for your reply. Can you point out which IEC publication indicates this?

In advance thanks.

Jairo

 

[7anoter4]

I think the EN 50522/2010 Annex O describes what it is called Global Earthing System. However, it is not a requirement but a recommendation:
"In order to identify such areas, no simple or stand-alone rule is available."
That means you have to check the touch and step potential in any case in order to avoid the transferred potentials.
IEEE 80/2013 17.8 Separate grounds states:
“The practice of having separate grounds within a substation area is rarely used for the following reasons”