3000 Series Vacuum Fault Interrupter The Trayer 3000 Series is the second generation VFI patterned from the 2000 Series. This vacuum fault interrupter is smaller in size, more economical and available in either liquid or SF6 insulation. The 3000 Series VFI provides three-phase, full-range circuit protection for underground distribution feeders at strategic locations where the protection is most effective. It can be supplied as a complete system that is totally self-contained. Installation is accomplished by merely connecting incoming and outgoing high voltage cables to their respective bushings. The 3000 Series VFI is available for 15 and 25 kV submersible, vault or padmount applications.