Resolution
The Square D Split Core Current Transformers (CT)  600 V Series single ratio, output 5 A in the secondary, up to 600 V, and are for indoor used. More detail on their technical specifications can be found in the attached Datasheets. See the Square D Instrument Transformer on page 41, as well as on Square D Instrument 600 Volt Class Section 6 Transformers on page 13. Open the files attached below.
The maximum voltage without additional insulation is 600 V ac. Do not apply 600 V class current transformers to circuits measuring phase-to-phase voltage greater than 600 V, unless adequate additional insulation is applied between the primary conductor and the current transformers. Square D assumes no responsibility for damage of equipment or personal injury caused by transformers operated on circuits above their published ratings.
Therefore, the split core current transformer 600 V series can be used in uninsulated bus for voltage less or equal to 600 V as said above.