Global grounding of HV and LV

[radag]

Good morning,

I come from the IEC world but usually do grounding grid calculations following IEEE 80-2000.

I have been reading through IEEE standards for some information about how to procceed when you have a distribution transformer substation. I mean:
for the transformer primary voltage, you design a ground grid for safe touch and step voltages as of IEEE 80-2000.
But then, you have the grounding of the neutral of the transformer secondary:
-What to do with it?
-Connect to the same ground as the HV grounding grid?
-Connect to a different ground?

In IEC world, both options are possible. I have a CENELEC document which addresses it, but I have not found anything about it in IEEE.
Any reference about it?

Thanks.

 

[Smart $]

Good morning,

I come from the IEC world but usually do grounding grid calculations following IEEE 80-2000.

I have been reading through IEEE standards for some information about how to procceed when you have a distribution transformer substation. I mean:
for the transformer primary voltage, you design a ground grid for safe touch and step voltages as of IEEE 80-2000.
But then, you have the grounding of the neutral of the transformer secondary:
-What to do with it?
-Connect to the same ground as the HV grounding grid?
-Connect to a different ground?

In IEC world, both options are possible. I have a CENELEC document which addresses it, but I have not found anything about it in IEEE.
Any reference about it?

Thanks.

Distribution substations are generally outside the purview of the NEC. However, when they are, TTBOMK it does not specifically require one or the other.

 

[radag]

More information?

More information?

Dear Smart$,

Thanks for the answer. About transformer substations, perhaps I did not use the proper name (I am not from an english speaking country). I mean, when power consumption is high, customers are fed in MV (4,16 kV in USA I think) instead of LV, and in those cases the 4,16 kV / 480 V transfomer is property of the customer. What is the grounding practice in those cases? I mean, the location of the transformer will have a grounding grid as of IEEE 80-2000 so that in case that a 4,16 kV phase-to-ground fault occurs, touch and step voltages are below tolerable limits. And what is done with the transformer secondary neutral? Put it to the same ground as 4,16 kV? And the bonding of the active parts (LV) of the transformer location? Bonded to 4,16 kV grounding grid or to the neutral grounding of 480 V in case it is independent from 4,16 kV?
Could you recommend any book, guide, standard which discusses this particular topic?

Thanks.

 

[jim dungar]

You are basically correct on your understanding of ground grids for step and touch potential. These grids are commonly built to power company specifications even though the customer may actually own the equipment.

LV grounding grids are used primarily for lightning systems and to create an equipotential reference point for bonding non-current carrying metallic surfaces (i.e. building steel, process piping, and equipment enclosures).

All grids are always bonded to each other.

 

[Smart $]

Dear Smart$,

Thanks for the answer. About transformer substations, perhaps I did not use the proper name (I am not from an english speaking country). I mean, when power consumption is high, customers are fed in MV (4,16 kV in USA I think) instead of LV, and in those cases the 4,16 kV / 480 V transfomer is property of the customer. What is the grounding practice in those cases? I mean, the location of the transformer will have a grounding grid as of IEEE 80-2000 so that in case that a 4,16 kV phase-to-ground fault occurs, touch and step voltages are below tolerable limits. And what is done with the transformer secondary neutral? Put it to the same ground as 4,16 kV? And the bonding of the active parts (LV) of the transformer location? Bonded to 4,16 kV grounding grid or to the neutral grounding of 480 V in case it is independent from 4,16 kV?
Could you recommend any book, guide, standard which discusses this particular topic?

Thanks.

FWIW, I understood you the first time :smile:

From my personal experience, most such systems utilize the same grounding grid. Whether intentionally or inadvertently I can't say.

Can't offer anything more. Perhaps someone else can...