400Hz Frequency Convertors

[KMeni]

We have two existing 90KVA 208V 3Ph Frequency Convertors in a Air Craft Hanger Bay. Are we to assume each Frequency Convertor is like a separate service and install separate grounding electrodes for each Frequency Convertor?? What Code section is relevant to this installation?

 

[SG-1]

Look at 250.30 for Seperately Derived Systems.

Section 250.30(A)(4)(a) covers more than one system on a common grounding electrode.