Neutral Grounding Reactors

The Neutral Grounding Reactor (NGR) is a single-phase reactor used in three-phase power systems. It is typically connected between the neutral point of a transformer or generator and ground, with the primary function of controlling single-line-to-ground faults to a predetermined level. This is achieved through its inductive impedance, which restricts the flow of fault current.

The key purposes of the NGR include:

l Limiting line-to-ground fault current to a level that prevents damage to power system equipment.

        l Mitigating transient overvoltages that may occur during the interruption of instantaneous fault currents.

l Allowing sufficient fault current to flow to ensure reliable operation of protective relays, thereby enabling prompt fault detection and clearance.

Under normal operating conditions, the voltage across the neutral grounding reactor remains low, resulting in minimal current flow. During a fault, however, the current increases significantly. The reactor must therefore be designed to withstand this elevated current for a specified duration, typically expressed in seconds, to ensure system stability and protection coordination.