Everything I can find indicates that CO2 is non-conductive, and recomended for electrical fires at all voltage levels. It is stored in liquid form, but discharged in gaseous form.
ABC indicates the type of fires that the extinguisher can be used to extinguish, not the specific agent.
C indicates that the agent is non-conductive, and suitable for electrical fires.
CO2 is rated BC, for flamable liquids and electrical fires.
You may be thinking of class K extinguishers, which are specially formulated for kitchen grease fires, but the agent may be conductive.
