Undervoltage Phase-fault Detection is provided by the Type CFV12 relay and is used in preference to the Type ICR when high-speed operation is desired. The drop-out on a phase-to-phase fault will be approximately 20 percent lower than the calibrated dropout on a 3-phase fault. Where more accurate fault detection is required, it is recommended that three single-phase Type CFV16A relays be used. They will have the same dropout on single-or three-phase faults.
