The distribution transformer is usually of Dyn11 vector group, since the single phase distributed loads will be far from ideal condition, in the sense there will always be unbalance between the loading of each phases, resulting in an unbalance of LV side neutral due to all the unbalanced loads at a moment. It means that the LV neutral will have a resultant zero sequence current flowing into its neutral point at the transformer. This will cause a shifting of the neutral point voltage too. The zero sequence current will be trapped inside the delta winding on the HV side of the distribution transformer and thus the propagation of zero sequence current towards the source is prevented. The delta winding is hence said to have a have a circulating zero sequence current that is trapped in the delta, i.e, It will not be reflected in the primary side of the transformer(the CTs at the HV side of the distribution transformer will not see it as they are not installed in the transformer usually). If the HV winding was of star type, instead of delta, the an HV equivalent of the LV zero sequence current will flow though the HV side neutral of the distribution transformer towards the source (i.e towards the substation transformer that feeds the distribution transformer). This would cause the protective relay to pick up and possibly trip the CB, in case if there is enough unbalance in the loads in the star connected secondary side. In order to prevent these unwanted trippings, the distribution transformer is selected as of Dy11 vector group. Similarly in a generator transformer, the outputs from the generator transformer (GT) is Star connected. It means whenever there is a fault or unbalance in the load side (ie. on the HV side of the GT, which will be the load side), it will cause a zero sequence current to be generated in the star point of the GT's HV side, for the protective relays of the GT's HV side to pickup and even trip. In normal case this would not happen. So in case there is an unbalance or fault in the the GT's LV side, which is connected in delta will have a circulating zero sequence current, which will NOT be permitted to go further upstream into the generator stator. The generator stator would have had to accept the zero sequence currents, had the GT's LV side been Star connected. This would cause zero sequence component of current and some negative sequence current in the stator. Negative sequence component would cause rotor heating. Zero sequence current will be flowing into the generator neutral also, causing the Earth fault relay of the Generator to pick and even trip in case of enough unbalances due to the faults on the HV side. (This could be possible in case of a single phase auto reclosing event at the GT's secondary side, after a fault occurance). So , the GT's LV in delta configuration prevents the load unbalances in the secondary sides from propagating to stator. Also, it suppresses the various harmonics from load side from propagating upstream. I hope this explanation gives an idea now!
Dyn11 means neutral is grounded at Y side, Dy11 means neutral is open grounded at Y side. Here 11, indicates LV side voltage and current are 30 lagging to HV.
Usually the subscript 1 is found on terminals.. like 1U1,1V1 & 1W1 (primary side)and 2U1, 2V1 & 2W1 (secondary).. I guess it varies from country to country.
Very good presentation. Need more lectures on Switchgear and testing relays
Great! Thanks for the knowledge Sir.
6:13 how did you got the diagram with Vbn, Vcn and Van pls explain!!!!
Amazing work! Thank you for sharing this great knowledge
Thanks a lot.
The explanation with slides are amazing.
👍👍👍
Excellent lecture
Excellent session sir!
Excellent explained
Thank you!
Very good. Thanks 🙏🙏🙏🙏🙏🙏
Sir it's 30 degrees leading or 330 degrees legging? You told in this video it's 30 leading. I m very confused sir plz explain
30 degree leading and 330 degree lagging are the same.
Please tell me about Dy9 configuration please
How test Vector group Yd5 or Dy5 transformer vector group test
Superb
Distribution transformer is generally of Dyn11. But generator transformer is Ynd1. Why it is so
The distribution transformer is usually of Dyn11 vector group, since the single phase distributed loads will be far from ideal condition, in the sense there will always be unbalance between the loading of each phases, resulting in an unbalance of LV side neutral due to all the unbalanced loads at a moment. It means that the LV neutral will have a resultant zero sequence current flowing into its neutral point at the transformer. This will cause a shifting of the neutral point voltage too. The zero sequence current will be trapped inside the delta winding on the HV side of the distribution transformer and thus the propagation of zero sequence current towards the source is prevented. The delta winding is hence said to have a have a circulating zero sequence current that is trapped in the delta, i.e, It will not be reflected in the primary side of the transformer(the CTs at the HV side of the distribution transformer will not see it as they are not installed in the transformer usually). If the HV winding was of star type, instead of delta, the an HV equivalent of the LV zero sequence current will flow though the HV side neutral of the distribution transformer towards the source (i.e towards the substation transformer that feeds the distribution transformer). This would cause the protective relay to pick up and possibly trip the CB, in case if there is enough unbalance in the loads in the star connected secondary side. In order to prevent these unwanted trippings, the distribution transformer is selected as of Dy11 vector group. Similarly in a generator transformer, the outputs from the generator transformer (GT) is Star connected. It means whenever there is a fault or unbalance in the load side (ie. on the HV side of the GT, which will be the load side), it will cause a zero sequence current to be generated in the star point of the GT's HV side, for the protective relays of the GT's HV side to pickup and even trip. In normal case this would not happen. So in case there is an unbalance or fault in the the GT's LV side, which is connected in delta will have a circulating zero sequence current, which will NOT be permitted to go further upstream into the generator stator. The generator stator would have had to accept the zero sequence currents, had the GT's LV side been Star connected. This would cause zero sequence component of current and some negative sequence current in the stator. Negative sequence component would cause rotor heating. Zero sequence current will be flowing into the generator neutral also, causing the Earth fault relay of the Generator to pick and even trip in case of enough unbalances due to the faults on the HV side. (This could be possible in case of a single phase auto reclosing event at the GT's secondary side, after a fault occurance). So , the GT's LV in delta configuration prevents the load unbalances in the secondary sides from propagating to stator. Also, it suppresses the various harmonics from load side from propagating upstream. I hope this explanation gives an idea now!
@@rjshtk Amazing
@@rjshtk thank you
very goodddd
what is the difference between Dyn11 and Dy11
Dyn11 means neutral is grounded at Y side, Dy11 means neutral is open grounded at Y side. Here 11, indicates LV side voltage and current are 30 lagging to HV.
@@sakthidhasan3764 About the grounding part your explanation is fine. But 11 means, the LV side voltages and currents are leading HV by 30 degrees.
I think Dyn11 and Dy11 are the same but on Dyn11 the neutral is brought out unlike Dy11 where neutral is not considered at any point
I think Dy1 is wrong phasor digram
Your connection is not matching with IS 2026 Part 1
it is standard practise to bring Terminals with subscript 2 are brought out or connection terminals, you have shown reverse to it
Usually the subscript 1 is found on terminals.. like 1U1,1V1 & 1W1 (primary side)and 2U1, 2V1 & 2W1 (secondary).. I guess it varies from country to country.