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understandingtransformervectorgroup-180629014651.pptx

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Satish Pydimarla
Satish Pydimarla

1) The document discusses transformer vector groups, which indicate the winding configurations and phase angle differences between primary and secondary windings. 2) For a Yd1 transformer, the secondary voltage leads the primary voltage by 30 degrees. However, if the terminal markings are changed, the vector group can change (e.g. to Yd5). 3) For positive sequence currents in a Yd1 transformer, the secondary currents lead the primary currents by 30 degrees. But for negative sequence currents, the secondary currents lag the primary currents by 30 degrees.

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Transformer Vector Group & Its Effect on Phase Shift of +Ve and –Ve phase sequence current component between secondary and primary
Understanding Transformer Vector Group â–  â–  â–  â–  Transformer is magnetically coupled circuit Its primary and secondary voltages either in phase or out of phase To say them in phase or out of phase will all depend upon polarity considerations Before to discussing polarity we will see something about notational basics of electricity
Transformer as magnetically coupled device This transformer is drawn such that whenever current enters from top side of Primary, exits from top side of the secondary Think about emphasize on the word drawn
Transformer as magnetically coupled device This transformer is drawn such that whenever current enters from top side of Primary, exits from Bottom side of the secondary Think about emphasize on the word drawn
Polarity Marking on Transformer A B a b A’ B’ a’ b’ The facts in previous slides can be represented in more simplistic way by polarity marking as below in figure A and Figure B respectively Figure - A Figure - B
Polarity Marking on Transformer â–  As for as one single phase transformer considered polarity marking carries a little meaning. Thus you will never see such polarity marking on single phase transformer. But if you want to connect these single phase transformer for a particular purpose. Then this polarity marking are much use full
Vector diagram for single phase transformer - 1 A B a b VAB Vab Voltage of a wrt b is in phase with voltage of A wrt B
Vector diagram for single phase transformer - 2 VA’B’ A’ B’ a’ b’ Voltage of a’ wrt b’ is out of phase with voltage of A’ wrt B’ Vb’a’ a’ at arrow tail and b’ at arrow head Vb’a’ . arrow direction is reverse to that of physical arrow marking near secondary coil and is in phase with primary voltage. To resolve such confusion use consistent Vcoa’nb’ventionand references as in previous slide
Polarity marking on transformer ■ Consider a simple case of paralleling the transformer in figure A and B. A B a b A ’ B ’ a ’ b ’ Connect like polarity
Kirchhoff's voltage law (KVL) â–  The directed sum of the electrical potential differences (voltage) around any closed circuit must be zero. (http://en.wikipedia.org/wiki/Kirchhoff %27s_circuit_laws) as on 11/09/10
Polarity marking on transformer â–  Consider another case of voltage doubling by using both transformer as from figure A B A a b A B a b Connect dislike polarity X Y L
Apply KVL Apply KVL starting from point L and traverse the loop anti clockwise with convention that voltage mentioned by double subscript notation with arrow head wrt tail traversed in the direction of arrow is +Ve else -Ve VXY – Vab – Vab = 0 VXY = Vab + Vab VAB Vab Vab VXY w
■ Consider yet another case of voltage doubling by using one transformer as figure A and other as figure B A B a b A’ B’ a’ b’ Connect dislike polarity X Y L
Apply KVL VXY - Vab – Vb’a’ = 0 VXY = Vab+ Vb’a’ Vab Va’b’ Vb’a,’ VXY w
Polarity of the transformer If a transformer is considered as black box this fact can be shown by a dot on respective terminal of primary and secondary. Here voltage Vab is considered to be in phase with VAB
Transformer redefined once again to avoid confusion between HV/LV and Primary/ Secondary (useful while defining vector group) (From http://en.wikipedia.org/wiki/Transformer 13/09/10) â–  â–  A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction. â–  If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows: (Power Flows From Primary To Secondary) Vs Ns ---- = ----- Vp Np
(From http://en.wikipedia.org/wiki/Vector_group 13/09/10) A Vector group is the International Electro technical Commission (IEC) method of categorizing the primary and secondary winding configurations of three-phase transformers. Within a polyphase system power transformer it indicates the windings configurations and the difference in phase angle between them. Transformer Vector Group
The point of confusion is in how to use this notation in a step-up transformer. As the IEC60076-1 standard has stated, the notation is HV-LV in sequence. For example, a step-up transformer with a delta-connected primary (LV), and star-connected secondary (HV), is not written as 'dY11‘, but 'Yd1'. The 1 indicates the LV winding lags the HV by 30 degrees. Transformer Vector Group
Vector Group of Step-Up Transformer Power Flow Secondary HV Primary LV dY11 LV Can’t be reference Yd1 Select HV as reference
Transformer Vector Group â–  Depends upon Polarity as well as external terminal marking â–  â–  â–  â–  Because phase difference between two magnetically coupled circuit is either 180 or 0 Hence whenever IEC specifies phase difference it shall be treated as with respect to line voltages Hence terminal marking is affecting on vector group and important If external terminal marking changed Yd11 group may become Yd5
3 Phase Supply Review Vb Vy Vry Vr Vyb Vbr
With this back ground now we are ready to understand transformer connections for Yd11 Transformer
Throughout this example instead of labels, colors are used purposely Let the 3 ph. Transformer individual windings are connected as shown in fig-A so as to form HV side Y and LV side delta. This transformer is redrawn in fig-B so as to make it easy to account for shift of 120 deg. between individual phases. Note the associated limb colors in primary and secondary of fig-A and Fig-B. Associated limbs are kept parallel in Fig-B. External leads of secondary are of Red, Yellow, Blue, different color than that of limb Color Red, Yellow, Blue carries normal meaning of Vr,Vy,Vb Fig-A Fig-B
By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color and direction Dark Yellow limb voltage of LV (Reversed) is line (R phase to Y phase) voltage Teal limb voltage of LV (Reversed) is line (Y phase to B phase) voltage Brown limb voltage of LV (Reversed) is line (B phase to R phase) voltage 12 O'clock 11 O'clock
As stated previously transformer vector group depends up on its terminal marking. How it happens we will see in next 2 slides (This type of connections are ANSI standard) We may call it as Yd5 Transformer
Change the terminal marking in respect of secondary such that in front of R Ph of primary there shall be Yellow phase of secondary and so on. Revised drawing is shown below Fig-A Fig-B
By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color and direction Dark Yellow limb voltage of LV (Reversed) is line (Y phase to B phase) voltage Teal limb voltage of LV (Reversed) is line (B phase to R phase) voltage Brown limb voltage of LV (Reversed) is line (R phase to Y phase) voltage 12 O'clock 5 O'clock
Most commonly used vector groups â–  Dy1 â–  Yd1 â–  Dy5 â–  Yd5 â–  Dy11 â–  Yd11
Connections for Yd1 T/F Here connections of Yd1 transformer are described to demonstrate effect of polarity of delta connections on transformer vector group
Change the connections of delta with respect to it’s polarity Fig-A Fig-B
By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color only shown doted to indicate it out of phase wrt HV Dark Yellow limb voltage of LV is line (Y phase to B phase) voltage Teal limb voltage of LV is line (B phase to R phase) voltage Brown limb voltage of LV is line (R phase to Y phase) voltage 5 O'clock Final Results 1800 to compensate for out of phase primary and secondary 12 O'clock
Or instead of shifting R Ph secondary voltage at last stage, we will redraw the same by different way so that primary and secondary windings shall have similar arrow markings ( may call as a tricky way)
Change the connections of delta with respect to it’s polarity Fig-A Fig-B
By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color only Dark Yellow limb voltage of LV is line (Y phase to B phase) voltage Teal limb voltage of LV is line (B phase to R phase) voltage Brown limb voltage of LV is line (R phase to Y phase) voltage 12 O'clock 1 O'clock
For the standard Yd1 transformer discussed previously now we will check relationship between +Ve and –Ve sequence currents reflected on primary with respect to that of on secondary
Let the power flows from Y side to D side. Show the currents instead of voltages Fig-A Fig-B
Note : Primary Y Winding currents shown out of phase wrt secondary. However source currents follows secondary limb current. C Apply KCL at point C Secondary R Ph Line Current + Teal Limb Current = Brown Limb Current Secondary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IS ` Di IP Yi For Yd1 Transformer with Y as primary and D as secondary Y Side Line Currents Leads D side Line Current by 300
Let the power flows from D side to Y side. Show the currents instead of voltages Fig-A Fig-B
Note: Secondary load current follows secondary winding current C Apply KCL at point C Primary R Ph Line Current + Teal Limb Current = Brown Limb Current Primary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IP For Yd1 Transformer with D as primary and Y as secondary Y Side Line Currents Leads D side Line Current by 300 ` Di IS Yi
To check the situation for –Ve sequence currents of Yd1 transformer let its source is replaced by RBY source hence new circuit will be
Let the power flows from Y side to D side. Show the currents instead of voltages and interchange Y and B limb in primary. Redraw secondary Fig-A Fig-B
Note : Primary Y Winding currents shown out of phase wrt secondary. However source currents follows secondary limb current. Apply KCL at point C Secondary R Ph Line Current + Teal Limb Current = Brown Limb Current Secondary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IP2 ` IS2 Di Yi For Yd1 Transformer with Y as primary and D as secondary For –Ve Sequence Y Side Line Currents lags D side Line Current by 300 Fig-B
Results of Yd11 and Yd1 for +Ve sequence and –Ve sequence are tabulated as below For Yd1 transformer Y side current leads D side current by 300 For Yd11 transformer Y side current lags D side current by 300 For +Ve sequence current component For -Ve sequence current component Y side current lags D side current by 300 Y side current leads D side current by 300
a b c A B C N A shortcut to identify vector group 12 O’Clock 1 O’Clock Yd1
Yd1 and Dy11 are duels A B C a b c a b c n N A B C D Yy d1 11
understandingtransformervectorgroup-180629014651.pptx

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understandingtransformervectorgroup-180629014651.pptx

  • 1. Transformer Vector Group & Its Effect on Phase Shift of +Ve and –Ve phase sequence current component between secondary and primary
  • 2. Understanding Transformer Vector Group â–  â–  â–  â–  Transformer is magnetically coupled circuit Its primary and secondary voltages either in phase or out of phase To say them in phase or out of phase will all depend upon polarity considerations Before to discussing polarity we will see something about notational basics of electricity
  • 3. Transformer as magnetically coupled device This transformer is drawn such that whenever current enters from top side of Primary, exits from top side of the secondary Think about emphasize on the word drawn
  • 4. Transformer as magnetically coupled device This transformer is drawn such that whenever current enters from top side of Primary, exits from Bottom side of the secondary Think about emphasize on the word drawn
  • 5. Polarity Marking on Transformer A B a b A’ B’ a’ b’ The facts in previous slides can be represented in more simplistic way by polarity marking as below in figure A and Figure B respectively Figure - A Figure - B
  • 6. Polarity Marking on Transformer â–  As for as one single phase transformer considered polarity marking carries a little meaning. Thus you will never see such polarity marking on single phase transformer. But if you want to connect these single phase transformer for a particular purpose. Then this polarity marking are much use full
  • 7. Vector diagram for single phase transformer - 1 A B a b VAB Vab Voltage of a wrt b is in phase with voltage of A wrt B
  • 8. Vector diagram for single phase transformer - 2 VA’B’ A’ B’ a’ b’ Voltage of a’ wrt b’ is out of phase with voltage of A’ wrt B’ Vb’a’ a’ at arrow tail and b’ at arrow head Vb’a’ . arrow direction is reverse to that of physical arrow marking near secondary coil and is in phase with primary voltage. To resolve such confusion use consistent Vcoa’nb’ventionand references as in previous slide
  • 9. Polarity marking on transformer â–  Consider a simple case of paralleling the transformer in figure A and B. A B a b A ’ B ’ a ’ b ’ Connect like polarity
  • 10. Kirchhoff's voltage law (KVL) â–  The directed sum of the electrical potential differences (voltage) around any closed circuit must be zero. (http://en.wikipedia.org/wiki/Kirchhoff %27s_circuit_laws) as on 11/09/10
  • 11. Polarity marking on transformer â–  Consider another case of voltage doubling by using both transformer as from figure A B A a b A B a b Connect dislike polarity X Y L
  • 12. Apply KVL Apply KVL starting from point L and traverse the loop anti clockwise with convention that voltage mentioned by double subscript notation with arrow head wrt tail traversed in the direction of arrow is +Ve else -Ve VXY – Vab – Vab = 0 VXY = Vab + Vab VAB Vab Vab VXY w
  • 13. â–  Consider yet another case of voltage doubling by using one transformer as figure A and other as figure B A B a b A’ B’ a’ b’ Connect dislike polarity X Y L
  • 14. Apply KVL VXY - Vab – Vb’a’ = 0 VXY = Vab+ Vb’a’ Vab Va’b’ Vb’a,’ VXY w
  • 15. Polarity of the transformer If a transformer is considered as black box this fact can be shown by a dot on respective terminal of primary and secondary. Here voltage Vab is considered to be in phase with VAB
  • 16. Transformer redefined once again to avoid confusion between HV/LV and Primary/ Secondary (useful while defining vector group) (From http://en.wikipedia.org/wiki/Transformer 13/09/10) â–  â–  A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction. â–  If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows: (Power Flows From Primary To Secondary) Vs Ns ---- = ----- Vp Np
  • 17. (From http://en.wikipedia.org/wiki/Vector_group 13/09/10) A Vector group is the International Electro technical Commission (IEC) method of categorizing the primary and secondary winding configurations of three-phase transformers. Within a polyphase system power transformer it indicates the windings configurations and the difference in phase angle between them. Transformer Vector Group
  • 18. The point of confusion is in how to use this notation in a step-up transformer. As the IEC60076-1 standard has stated, the notation is HV-LV in sequence. For example, a step-up transformer with a delta-connected primary (LV), and star-connected secondary (HV), is not written as 'dY11‘, but 'Yd1'. The 1 indicates the LV winding lags the HV by 30 degrees. Transformer Vector Group
  • 19. Vector Group of Step-Up Transformer Power Flow Secondary HV Primary LV dY11 LV Can’t be reference Yd1 Select HV as reference
  • 20. Transformer Vector Group â–  Depends upon Polarity as well as external terminal marking â–  â–  â–  â–  Because phase difference between two magnetically coupled circuit is either 180 or 0 Hence whenever IEC specifies phase difference it shall be treated as with respect to line voltages Hence terminal marking is affecting on vector group and important If external terminal marking changed Yd11 group may become Yd5
  • 21. 3 Phase Supply Review Vb Vy Vry Vr Vyb Vbr
  • 22. With this back ground now we are ready to understand transformer connections for Yd11 Transformer
  • 23. Throughout this example instead of labels, colors are used purposely Let the 3 ph. Transformer individual windings are connected as shown in fig-A so as to form HV side Y and LV side delta. This transformer is redrawn in fig-B so as to make it easy to account for shift of 120 deg. between individual phases. Note the associated limb colors in primary and secondary of fig-A and Fig-B. Associated limbs are kept parallel in Fig-B. External leads of secondary are of Red, Yellow, Blue, different color than that of limb Color Red, Yellow, Blue carries normal meaning of Vr,Vy,Vb Fig-A Fig-B
  • 24. By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color and direction Dark Yellow limb voltage of LV (Reversed) is line (R phase to Y phase) voltage Teal limb voltage of LV (Reversed) is line (Y phase to B phase) voltage Brown limb voltage of LV (Reversed) is line (B phase to R phase) voltage 12 O'clock 11 O'clock
  • 25. As stated previously transformer vector group depends up on its terminal marking. How it happens we will see in next 2 slides (This type of connections are ANSI standard) We may call it as Yd5 Transformer
  • 26. Change the terminal marking in respect of secondary such that in front of R Ph of primary there shall be Yellow phase of secondary and so on. Revised drawing is shown below Fig-A Fig-B
  • 27. By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color and direction Dark Yellow limb voltage of LV (Reversed) is line (Y phase to B phase) voltage Teal limb voltage of LV (Reversed) is line (B phase to R phase) voltage Brown limb voltage of LV (Reversed) is line (R phase to Y phase) voltage 12 O'clock 5 O'clock
  • 28. Most commonly used vector groups â–  Dy1 â–  Yd1 â–  Dy5 â–  Yd5 â–  Dy11 â–  Yd11
  • 29. Connections for Yd1 T/F Here connections of Yd1 transformer are described to demonstrate effect of polarity of delta connections on transformer vector group
  • 30. Change the connections of delta with respect to it’s polarity Fig-A Fig-B
  • 31. By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color only shown doted to indicate it out of phase wrt HV Dark Yellow limb voltage of LV is line (Y phase to B phase) voltage Teal limb voltage of LV is line (B phase to R phase) voltage Brown limb voltage of LV is line (R phase to Y phase) voltage 5 O'clock Final Results 1800 to compensate for out of phase primary and secondary 12 O'clock
  • 32. Or instead of shifting R Ph secondary voltage at last stage, we will redraw the same by different way so that primary and secondary windings shall have similar arrow markings ( may call as a tricky way)
  • 33. Change the connections of delta with respect to it’s polarity Fig-A Fig-B
  • 34. By resemblance from previous sheet Transform to resemble with 3 Ph review taken previously. Notice the changes in vector diagram for color only Dark Yellow limb voltage of LV is line (Y phase to B phase) voltage Teal limb voltage of LV is line (B phase to R phase) voltage Brown limb voltage of LV is line (R phase to Y phase) voltage 12 O'clock 1 O'clock
  • 35. For the standard Yd1 transformer discussed previously now we will check relationship between +Ve and –Ve sequence currents reflected on primary with respect to that of on secondary
  • 36. Let the power flows from Y side to D side. Show the currents instead of voltages Fig-A Fig-B
  • 37. Note : Primary Y Winding currents shown out of phase wrt secondary. However source currents follows secondary limb current. C Apply KCL at point C Secondary R Ph Line Current + Teal Limb Current = Brown Limb Current Secondary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IS ` Di IP Yi For Yd1 Transformer with Y as primary and D as secondary Y Side Line Currents Leads D side Line Current by 300
  • 38. Let the power flows from D side to Y side. Show the currents instead of voltages Fig-A Fig-B
  • 39. Note: Secondary load current follows secondary winding current C Apply KCL at point C Primary R Ph Line Current + Teal Limb Current = Brown Limb Current Primary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IP For Yd1 Transformer with D as primary and Y as secondary Y Side Line Currents Leads D side Line Current by 300 ` Di IS Yi
  • 40. To check the situation for –Ve sequence currents of Yd1 transformer let its source is replaced by RBY source hence new circuit will be
  • 41. Let the power flows from Y side to D side. Show the currents instead of voltages and interchange Y and B limb in primary. Redraw secondary Fig-A Fig-B
  • 42. Note : Primary Y Winding currents shown out of phase wrt secondary. However source currents follows secondary limb current. Apply KCL at point C Secondary R Ph Line Current + Teal Limb Current = Brown Limb Current Secondary R Ph Line Current = Brown Limb Current - Teal Limb Current & Brown limb current is primary current IP2 ` IS2 Di Yi For Yd1 Transformer with Y as primary and D as secondary For –Ve Sequence Y Side Line Currents lags D side Line Current by 300 Fig-B
  • 43. Results of Yd11 and Yd1 for +Ve sequence and –Ve sequence are tabulated as below For Yd1 transformer Y side current leads D side current by 300 For Yd11 transformer Y side current lags D side current by 300 For +Ve sequence current component For -Ve sequence current component Y side current lags D side current by 300 Y side current leads D side current by 300
  • 44. a b c A B C N A shortcut to identify vector group 12 O’Clock 1 O’Clock Yd1
  • 45. Yd1 and Dy11 are duels A B C a b c a b c n N A B C D Yy d1 11