Why zig zag connection of transformer is used?

Zig-Zag connection is the combination star and delta connection and it has the both advantage of a star and delta.

It can be used as earthing transformer in a delta connected (no neutral terminal) system or an ungrounded start connected (three terminal star) where in neutral is not available for grounding. The zig zag transformer used for earthing of delta connected transformer.

In delta connected transformer there will not be path to zero sequence components and no protection can be performed for these components which increases and stress and heating in the windings. The zig zag transformer provides a neutral for the proving a path to zero sequence components during line to ground fault and allows the protection to be operated due to this fault. In the obsence of grounded neutral, voltages of healthy would increase line to line voltage level, stressing the insulation connected to equipment. Thug Zig zag transformer not only helps in protection it also reduces the voltages stress under symmetrical fault conditions.

In power electronic converters the zig zag transformer is used to eliminate the DC magnetizing component presented due to improper firing angles. The improper firing angles of power electronic components (SCR) may introduce DC magnetizing component and this is canceled in each limb of zig zag transformer due to opposite direction of DC magnetizing component of currents flowing in the windings on the same limb.

Zig zag transformer offers low impedance path to zero sequence components under fault conditions so it can be perfectly used as earthing transformer with and earthing reference. If the earthing current has to be limited under fault conditions, a suitable resistor can be placed in zig zag neutral terminal.

[wp_ad_camp_1]

Harmonic voltages presented in system to some extent can be cancelled in zigzag windings due to opposite connection of winding coils.

A zig-zag transformer is used for providing grounding on the transformer. It provides insulation between the ground and the component so that the system component may not be affected by the fault currents. Zigzag transformer terminates the harmonics of the power system.

• Less Costly for grounding Purpose. It is typically the least costly than Y-D and Scott Transformer.
• Third harmonic suppression. The zigzag connection in power systems to trap triple harmonic (3rd, 9th, 15th, etc.) .
• Ground current isolation.
• No Phase Displacement.