Substation Control Building Grounding

What's an 'earthing mat' ?

I agree with you, redfred. It seems to me-according to o.p.term "earthing "- it has to be according to BS. However, it seems to me, for now, these standards are not so far from U.S. national standards in order to build an "earthing mat" according to BS EN 50522 or a"grounding grid" according to IEEE 80 and building[Uffer] grounding according to BS 7430 or NECA 331.

There is also the possibility that the AP is misusing one of the buzzwords in an attempt to look knowledgeable enough to ask such a question.

On that note, most modern substations do not have a control building because the substation is remotely controlled from a central site.

Truly you must live in a blessed country for every substation I have ever built, repaired or maintained had a control building which housed the metering, protection relays, remote control and other necessary equipment.

The opening and closing remote controls were interfaced with the local controls. The substation acted autonomously to protect its own equipment which is needed when the lines of communication are down.

As for the earth mat, now that is a term I am familiar with, for that is what we call them here. As for the requirements for the mat, then the end user may have their own specifications to suit their needs and there are appropriate standards which must be followed as a base line and may be exceeded with approval.

A construction substation for a power station required that the earth mat be 50mm x 6mm flat steel bar on 1m grid and welded at each crossover. It was specified that no copper be buried in the ground and all connection points to towers be able to be accessed through risers. The earth mat had to extend beyond the fence for a distance as specified to prevent step potential and be bonded to fence. All the earth mat trenches were to be filled with a suitable conductive clay.

There are standards that relate to the combined earth mat resistance.

For the building if it were on concrete slab then the earth mat will likely be connected to the floor and trench reinforcing and have a separate earth connection point to an earth bar inside the building and be clearly labeled as must all other earth connection points.

For earthing in mines then other provisions apply.

You need to ascertain what the end users earthing requirements are and ensure they comply with the relevant standards for your area.

Eggs are laid, people are laid, earthing mats/grids are installed. Please, go to a site that is being built and look. Then ask questions on that which puzzles you. That means leaving the seat you are on and venturing out into the world where stuff happens. It will be most educational and mind blowing.

If it is part of the concrete foundation it would make sense to do this first.

What do your local standards say?

Is there a Mentor at the facility that can answer these questions and review the design documentation or is this entirely a home-brew project being carried out by amateurs?