VT Guard is a preventive device against the ferroresonance phenomenon which may be triggered in power networks with ungrounded, or not directly grounded neutral point. The ferroresonant oscillations may be initiated in ungrounded networks by switching or other transient phenomena and pose a significant damage risk to phase-to-ground connected inductive voltage transformers.
VT Guard prevents voltage transformers against potential ferroresonant overcurrent by prompt damping action.
In comparison with other anti-ferroresonance devices, VT Guard is design to be selectively active against the ferroresonant oscillations while being inactive against natural system asymmetry resulting form phase imbalance or single phase ground faults.