arXiv:2611.08777v1 Announce Type: new Abstract: Fault-induced transfers of large data centers to backup supply can cause abrupt reductions in grid-served demand. Coordinating reactive-power support to mitigate these transfers requires consideration of facility-specific voltage--duration ride-through characteristics, particularly when support capacity is limited. This paper develops a ride-through-aware extension of quadratic voltage control that assesses voltage deviations relative to the admissible margins specified by these characteristics. We establish four design requirements that jointly express envelope-based severity, duration dependence, and preventive voltage-restoration incentives. Within a multiplicatively gated quadratic class, we derive necessary and sufficient conditions for satisfying these requirements and construct an explicit family of envelope-normalized objectives. We apply the proposed objectives to reactive-power coordination and evaluate their performance on the IEEE 14-bus, New England 39-bus, and NPCC 140-bus systems. Comparisons with Volt/VAR control, conventional nominal-voltage tracking, and recent data-center voltage-control methods demonstrate improved data-center retention under matched reactive-power support constraints. In the IEEE 14-bus study, the proposed controller reduces the mean data-center disconnection rate by 44.8\% and grid-demand loss by 27.4\% compared with the best-performing baseline. These results highlight the benefit of incorporating data-center ride-through requirements into reactive-power allocation.