Transformer vector group

🔌 Purpose of Vector Group Test

• Checks phase sequence and angular displacement between HV and LV windings.
• Confirms polarity of windings.
• Ensures compatibility for parallel operation of transformers.
• Prevents short circuits, circulating currents, and maloperation of protection systems.

A transformer vector group test verifies the phase displacement, polarity, and winding configuration of a transformer to ensure it can operate safely in parallel with others. It is essential during commissioning, factory acceptance, and maintenance to prevent circulating currents and synchronization issues

Transformer vector group

🛠️ Equipment Required

• Three-phase supply (usually applied to HV side).
• Voltmeter or potentiometric method for voltage ratio measurement.
• Phase angle meter (alternative method).
• Test leads and safety gear.

Transformer vector group

📝 Step-by-Step Procedure

1. Pre-checks: Ensure transformer is isolated, grounded, and safe to energize.
2. Apply 3-phase voltage to HV side.
3. Measure voltages between HV and LV terminals using voltmeter/potentiometric method.
4. Check polarity: Verify correct orientation of windings.
5. Plot phasor diagram: Use measured values to determine phase displacement.
6. Confirm vector group: Compare results with standard vector group notations (e.g., Dyn11, Yd1, YNyn0).

Transformer vector group

Transformer vector group

Vector Groups 5 Group-3

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Group 3: 30 degree lag phase displacement (Dy1, Yd1, Yz1)

1. Dy1: Delta — Star Connection
2. Yd1: Star — Delta Connection
3. Yz1: Star — Zig-zag Connection

Vector Groups 5 Group-4)

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Group 4: 30 degree lead phase displacement (Dy11, Yd11, Yz11)

1. Dy11: Delta — Star Connection
2. Yd11: Star — Delta Connection
3. Yz11: Star — Zig-zag Connection

Yd18 Star — Delta Connection

DdO Delta — Delta Connection