Ground Ring

[timm333]

NEC 250.52 (A)(4) allows ground-ring to be used as grounding-electrode. Some additional ground-rods might be required (and tied to the ground-ring) in order to strengthen the ground-ring. Which rule of NEC describes whether the additional ground-rods are required or not, and if required then what should be the spacing between these additional ground-rods? Thanks

 

[jumper]

250.53. Ground rings are covered in(F). Additional/supplemental grounding electrode not required for ground ring.

 

[timm333]

Thanks! Under what conditions the IEEE-80 calculations are required for ground-potential-rise; if we place the ground-ring around a steel structure as per NEC, then do we still need to do the IEEE-80 calculations for the grounding of this steel structure?

 

[bphgravity]

Codes and standards compliance is dictated by the law &/or the AHJ. In other words, the regulating body over the installation in question will identify compliance requirements.

 

[don_resqcapt19]

Are you building a substation? That is what IEEE-80 applies to. If so, I would expect that there would be engineered drawings to work from.

 

[timm333]

There will be substation with a transformer with MV primary and LV secondary. The steel structure is on the LV (downstream) side if the transformer, so I guess IEEE-80 would not apply for the grounding if the structure.

Another question: When we we connect the grogrounding ellectride

 

[timm333]

There will be substation with a transformer with MV primary and LV secondary. The steel structure is on the LV (downstream) side of the transformer, so I guess IEEE-80 would not apply for the grounding of the steel structure.

Another question: When we we connect the grounding conductor to steel structure by exothermic welding, what should be the specifications of this welding connections (minimum length of exothermic weld, etc.)

 

[Julius Right]

In my opinion, there are two possible dangerous faults:
1) the ground fault from the medium voltage system to the substation grounding grid.
2) the transferred potential through medium voltage cable shield or armor if these are grounded at the substation grid.
If the touch and step potentials are out of permissible limits then you have to isolate the termination and insulate the shield and armor at the rated voltage level.
The foundation grounding it is for inside potential equalization.
The low voltage ground fault does not participate on GPR rise since stay always on the grounding grid and the fault current does not pass through ground but only through grid conductors.

 

[timm333]

Does it mean that the IEEE-80 calculations should be done only in the case of Medium Voltage and High Voltage?

 

[timm333]

How about we do IEEE-80 calculations for MV area (substation), and put the simple ground-ring for the LV area (steel-structure), and then connect the ground-ring of the steel-structure to the ground-grid of the substation using a 4/0 conductor ?

 

[don_resqcapt19]

How about we do IEEE-80 calculations for MV area (substation), and put the simple ground-ring for the LV area (steel-structure), and then connect the ground-ring of the steel-structure to the ground-grid of the substation using a 4/0 conductor ?

My understanding is that under fault conditions, there can be a huge voltage on the substation equal potential grid as measured to remote earth. It is a good idea to connect the substation grounding system to the grounding system of a remote structure?

 

[GoldDigger]

It is not.
Yet another issue is that during a primary fault the earth currents may well cause a dangerous voltage gradient under the remote building.
It would be wise to treat all pipes, etc. that are in contact with the earth as "likely to become energized" and bond them to the house GES.
This includes even drain pipes that you might not otherwise bond.

 

[timm333]

Is exothermic welding allowed for the connection of two ground conductors (or a conductor with ground-rod), or should these connections be made using the grounding connectors?

 

[GoldDigger]

Is exothermic welding allowed for the connection of two ground conductors (or a conductor with ground-rod), or should these connections be made using the grounding connectors?

Exothermic welding is allowed almost anywhere.
In the case of a GEC which is required to be continuous, it and pressure splices are two of the allowed means of splicing the "continuous" conductor.
In the case of bonding jumpers that are part of the GES but are not identified as the GEC, irreversible splices are not required, but Cadweld is still, AFAIK, allowed as long as it is used in accordance with the kit instructions.

 

[timm333]

All equipment grounding conductors (conductors for the grounding of transformer, steel structure, motors, etc.) originate from a grounding bus-bar; this grounding bus-bar is also connected to the start point of the transformer. Should we use only one grounding bus-bar for the whole structure, or can a separate grounding bus-bar be used at every floor of the structure?

 

[don_resqcapt19]

Equipment grounding conductors are required to be run with the power circuit conductors and originate at the grounding bus in the panel that supplies the circuit conductors.