110.26 (A)(1) Mentions nominal voltage to ground 601v thru 1000v.
Can anyone give me an example of where I would find such high voltages to ground ?
And Don’t say utility.
Why would any facility use such high voltage to ground and what would be the application?
The reason we include up to 1000V to ground in this category, comes from the evolving technology of photovoltaic systems, increasing the voltage on the DC side of the system. It is only recently as of NEC2017, that 110.26 included any consideration for systems between 601V and 1000V. It used to be that you had to check the table in 110.34 to get this information. The same information always has been the same, it just moved to the table for 110.26, because of its practical application as a utilization voltage.
It is more economical to build systems that operate at higher voltages on the DC side, due to the higher voltages being more efficient at pushing power long distance. Voltage you "pay for" with plastic, while current you "pay for" with metal. The inverters also work more efficiently with processing power at higher voltages.
It used to be that the voltage was limited to 600V on the DC side between the modules and inverter, due to a lack of listed products for handling anything greater. As products began to exist that were capable of 1000V, 1500V, and 2000V, PV systems using these products, and taking credit for the increased voltage rating, began to be implemented in practice. 1500V is the highest I've seen in practice today, and is restricted to not be used on buildings. 1000V is the highest array voltage allowed on buildings at the moment.
A system that has an open circuit value up to 1500V between the polarities, would be an example with equipment at 750V to ground, presuming it is functionally grounded by means of a non-isolating inverter tied to a grounded AC grid. The negative polarity is 750V below ground, and the positive polarity is 750V above ground.
A system that has an open circuit voltage of 1000V, and has one polarity grounded, would be another example of up to 1000V to ground.
