Wye-Delta or Star-Delta Connection Transformers

Why Transmission Line Transformers are used as  Star-Delta or Star-Wye Connection? 

The main use of the star-delta or star-wye connection is at the substation end of the transmission line where the voltage is to be stepped down. 

The primary winding is wye (Y)-connected with grounded neutral as shown in the above figure-Connection Diagram of the Wye-Delta or Star-Delta Connection Transformers. 

The ratio between the secondary and primary line voltage is 1/ 3 times the transformation ratio of each trans-former. 

There is a 30° shift between the primary and secondary line voltages which means that a Y − ∆ transformer bank cannot be paralleled with either a Y − Y or a ∆ − ∆ bank. Also, third harmonic currents flow in  ∆ to provide a sinusoidal flux.

What Is The Difference Between A Star And A Delta Connection?

Star Connection	Delta Connection
1.     Line current = phase current	1.Line current = √3 × phase current
2.     Line voltage = √3 phase voltage	2.     Line Voltage = Phase Voltage
3.     Total power = √3 × VL × IL ×power factor	3.     Total power = √3 × VL × IL × power factor
4.     Phase voltage is √3 times less than the line voltage due to which the number of turns it takes to winding is less. This saves copper.	4.     Due to the same line voltage and phase voltage, the number of turns in the winding of this connection is high.
5.     Neutral is available in it.	5.     Which is not neutral.
6.     Due to the availability of neutral, 2 types of voltages are available such as 240 Volt phase voltage and 415 Volt line voltage. Hence the lighting load on a single phase and power load on 3 Phases can be added to this connection.	6.  Only 415 volt 3 Phase is available in this connection. For this reason, you cannot take a load of 1 single phase in it.
7.     In this the line voltage is 30° leading to this phase voltage.	7.     In this line current it is 30° leading from phase current.
8.     It has a lower breakdown voltage.	8. It has a low breakdown voltage.

Difference Between Star-Delta Connection and Star-Delta Starter

Hi guys, you may be confused hearing the star-delta connection!!

You may be read another topic with a star-delta connection like below:

Star-Delta Connection Using for Motor Starting

Star delta starters are another device that may be used to reduce current demand during motor startup. It is often used for starting three-phase induction motors, but can only be used when starting the motor without load and when the required starting current is relatively low....

So, it was a star-delta starter, which means a motor starter device.

But, this article is limited to a three-phase transformer connection for the power transmission network.