Substation Grounding System

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dello

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Hi,

I need some help here, i`m having some doubts regarding the grounding installation.

What is the difference between a ground grid and a ground plate?
Based on my understanding the ground grid are made out of parallel grounding electrodes connected together by copper tapes which forms the grounding grid, so wheres is this ground plate situated?

Another question, what is the difference between a earthing link chamber and a earthing inspection chamber?

Hope u guys can offer me some clarification, thanks alot :)
 
A grounding grid may be placed under the entire area around a substation with it's purpose to keep what you are standing on the same potential as all the grounded objects around you.


A grounding plate is just another type of electrode like a rod or a ring.

At least that is my understanding of it.
 
Thats what got me confused here,
Is it possible to have both grounding plate and grounding grid?

Tis is wat is in the drawing, isn't the grounding and equipment ground supposed to be interconnected?

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From the drawing it looks like the grid gets tied the GEC with an split bolt suitable for UG use, and the equipment earth (GEC, I presume) must be carried back to the neutral at the service???
 
Here is what I am used to seeing at industrial plant substations usually not higher than 13.8KV.We would build a grid on 2/0 on 10 to 15 foot centers and tie all equiment ground buses to this grid sometimes with 2/0 taps but usually #2 taps.The transformers support frames in the yard would also tie to this grid.This transformer yard grid limits could be inside the fence or outside the fence,there are some recommended distances involved with this that I have forgotten and the fence grounding would also tie to the grid.

The ring as we called them were internal to the substation and was usually a bare 2/0 routed around the inside of the building about 7 or 8 feet from the floor and all equipment sheet metal,cable tray etc would tie to this.This ring would have 4 drops one in each corner down to a ground plate and the plate would have a connection to the grid.We usually had 10 foot ground rods on 50 foot centers around the grid.The grid itself was tied together at the cross intersections with exothermic welds.

We sometimes would tie the grid to the plant grid in two places just to keep everything talking to each other but some clients wanted the substation isolated.

If there was sophisticated electronic equipment in the sub it would tie to a triad of rods at two points and spaced 10 foot apart with all rods tied together,one corner of this triad also tied to the grid but more often than not it too was isolated.

I don't recall to many of these 13.8 subs that had a need for touch potential protection as fault currents were not usually high enough per engineering to warrant it but when it was required by client and/or engineering then the grid spacing would be reduced to a 2 foot grid and a crushed stone of some sort would be used for back fill around the subsation.The realy high voltage subs of the POCO usually require touch and step potential protection.

Thats my bluirb and I'm sticking to it:)

dick
 
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