(Δ- Y):- the NGR is connected in delta (Δ) configuration, while the secondary winding is connected in star (Y) configuration. This connection provides a path for zero-sequence currents to flow to ground, effectively grounding the neutral point of the transformer.
(Δ-Z) : – the primary winding of the NGR is connected in delta (Δ) configuration. However, in this configuration, the secondary winding is connected in zigzag (Z) configuration. This connection is particularly suitable for ungrounded systems, as it allows for the detection and grounding of the zero-sequence currents in the system.
(Δ-Δ) :- In this configuration, both the primary and secondary windings of the NGR are connected in delta (Δ) configuration. This connection is less common and is typically used in special applications where a delta-delta configuration is preferred or required.
