A Technical Reference Paper Fault-Induced Delayed Voltage Recovery

A Delayed Voltage Recovery event, or more popularly today, a Fault Induced Delayed Voltage Recovery (FIDVR), is the phenomenon whereby system voltage remains at significantly reduced levels for several seconds after a transmission, subtransmission, or distribution fault has been cleared. Significant load loss due to motor protective device action can result, as can significant loss of generation, with a potential secondary effect of high system voltage due to load loss. A severe event can result in fast voltage collapse.

Therefore the Transmission Issues Subcommittee (TIS) provides the following definition: Fault-Induced Delayed Voltage Recovery — a voltage condition initiated by a fault and characterized by:
• Stalling of induction motors
• Initial voltage recovery after the clearing of a fault to less than 90 percent of precontingency voltage
• Slow voltage recovery of more than two seconds to expected post-contingency steadystate voltage levels

Although this phenomenon can occur on any voltage level, it becomes concerning when such events adversely impact the voltage recovery of the Bulk Electric System (BES). Further, if the BES voltage does not recover to 90 percent of the pre-contingency system voltage in a few seconds, the FIDVR can initiate further tripping of load and generation. Longer periods of depressed voltage below such levels can cause damage to customer and electric system
equipment.