Damaging transients on AC and DC power circuits can occur from any number of sources. The most common are due to lightning and switching transients. To counter the detrimental effects of transients, metal oxide varistors (MOVs) are typically connected in AC circuits across a mains supply in phase-to-neutral or phase-to-phase configurations to provide transient protection. For DC circuits, MOVs are connected positive-to-negative. MOVs are also used for maintaining DC voltage stabilization.