Active System Grounding With a Novel Distribution Transformer Design

Active System Grounding With a Novel Distribution Transformer Design

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A novel Wye-wye wickelfalzrohre transformer design for active system grounding, is described in this paper.Proposed as a solution to improve the ground fault performance in distribution line networks, the zero-sequence flux developed in the magnetic core of a transformer is on a ground fault harvested by coils wound around three limbs, or extra limb(s) in a Wye-wye transformer.Built with three limbs, and no tertiary winding, the flux developed in the core on a ground fault is forced to return through air, which has a high reluctance, but with four or more limbs, the flux circulates in the transformer magnetic core, which has a low reluctance.

Connected to one or more single-phase windings, the transformer neutral current is on a ground fault actively altered by fixed and switched load impedances.In theory, a ground fault arc is with a low current and delay in recovery voltage self-extinguishing, and no interruption in supply is required, but sustained, must be isolated.Proposed in this paper, for an active load marni shirt green switched grounding method, the neutral current on a sustained ground fault is increased to enable plain overcurrent and fuse protection to operate without the need of sensitive directional relay protection.