Vector Group of Transformers

The vector group of a transformer refers to the phase relationship between the primary and secondary windings of the transformer. It is used to describe the way in which the transformer behaves under different operating conditions, such as when it is used to transform voltage or current.

What is Gas Insulated Switchgear (GIS)?

What Do Vector Groups Mean in Transformers?

There are three different types of transformer connections, these are star, delta and zigzag.

Here are the explanations;

• Star Connection: Shown as “Y” there is neutral line in this connection type.
• Delta Connection: Shown as “D” there is no neutral line in this connection type.
• Zigzag Connection: Shown as “Z” it is used for transformers which have smaller power ratings. This connection is only made on the secondary side of the transformer. The primary side can be connected on either the star or delta.

How to Calculate the Group Angle in a Vector Group?

Group angle is known as the angle between primary and secondary winding in the same phase even if the transformer is monophase or three-phase. A constant is indicated by dividing group angle to 30 degrees. So, if you think of the opposite, when you multiply group angle with 30 degrees, you will obtain phase difference angle between voltages of the same phase. In vector groups, first letter is written in upper-case, second in lower-case. There are several different vector groups that can be used to describe the behavior of a transformer, including:

• Dyn11: The most used vector group in power transformers in the application of distribution systems. Primary windings are connected as Delta, secondary side as star (with neutral line).Voltage Phase difference in the same phase 30×11=330 degrees.
• Ynd11: Primary windings are connected as Star (with neutral line), secondary side as delta.Voltage Phase difference in the same phase 30×11=330 degrees.
• YnYn0: Primary windings are connected as star (with neutral line), secondary side as Star (with neutral line), Voltage Phase difference in the same phase is 0 degree.
• Yzn5: Primary windings are connected as star, secondary side as zigzag. Voltage phase difference in the same phase is 30×5=150 degrees.

The vector group of a transformer is typically specified by the manufacturer and is determined based on the intended use of the transformer. It is important to select the correct vector group for a transformer to ensure that it performs as expected under different operating conditions.

Schneider Electric Switchgear

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