2000 Series Vacuum Fault Interrupter The Trayer 2000 Series is the original vacuum fault interrupter (VFI) and is field-proven since 1981. It is the reliable workhorse of the industry. This vacuum fault interrupter 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 2000 Series VFI is liquid-insulated and available for 15, 25 and 35 kV systems.