Solar PV Array Grounding

[kmh1]

I am working on completing a ground potential rise and grounding study for a large 10 MW ground mounted PV installation. The site will be interconnected to the utility grid via a 44/12.5kV substation with the substation ground interconnected with the PV module grounding system. The 44kV system has no neutral or ground return. Prior to completing the modeling I wanted to determine whether it is common practice to install a buried ground grid conductor around each array support structure in order to address possible touch potentials transferred during substation HV ground faults? Our modeling will help us determine the potential hazards based on the soil resistivity but I just wanted to inquire about the common industry practices.

 

[7anoter4]

In my opinion it depends upon the distance between the two grounding grids. If the distance is relatively reduce at least two grounding cable has to be connected between. If there are units located on the same platform I shall use up to 4 cable-two at the ends and two in the middle of the front. If they are kilometers distance I don't think it could be effective.

 

[jghrist]

The concern for touch-potential at the array during a HV substation fault is valid. A detailed study could be made using software like SES SPLITS or FDIST to determine the transferred potential. It will depend on the grounding, length, and number of the 12.5 kV circuits. A perimeter ground wire at the array would be good insurance.

 

[kmh1]

Thank you, we are presently modeling the site using SES software. I was curious to see if installing a buried ground conductor around each array support was commonplace or just around the overall perimeter of the site. The SES software should uncover any hazards but the extra buried copper around each panel support would certainly add up cost-wise. We will plan to include the grounded steel support foundations in the model which will be a grounding benefit. The fact that the entire solar site would likely become covered in grass and weeds will definitely lower the tolerable touch potential values.