Medium Voltage 3 phase Transformer Terminals. 4

[Pdave6]

We have 3 phase 26.4kV Delta - 490 volt Delta and 490 volt Wye, 3 winding transformer which feed 12 pulse rectifier on 490 volt side, generating about 3 MW for Traction service. This oil filled transformer has nameplate but no markings at 26.4kV bushings for H1, H2 and H3. Similarly on secondary R1, R3 and R5 are Delta and R2, R4 and R6 are Wye bushings with no markings. My main concern is to find H1 bushing on primary.
1. Assuming I stand on 490 Volt bushings facing 26.4 kV bushings, which side is H1 bushing....on right hand side or left ?
Thanks in advance.
PD

 

[Pdave6]

I forgot to attach the transformer nameplate info. Here it is. Thanks.

 

[prc]

Left side- Please see C57.12.10 Standard

 

[Pdave6]

PRC,
Thank you.

 

[jghrist]

Left side- Please see C57.12.10 Standard

That's not how I read C57.12.10 Fig 3. If you are looking at the transformer from the high side, H1 is on the right. Assuming that the transformer is built per C57.12.10. C57.12.10 doesn't sllow for secondary bushings named R1, R2, R3, R4, R5, R6. The nameplate also shows it that way.

 

[thermionic1]

I have always looked at the tap changer as an orientation point from the nameplate. It hasn't failed me (yet).

 

[Pdave6]

Thank you JGHRIST.
It seems that Fig 3 -Bushing arrangement, matches with what PRC wrote (Left side is H1 bushing, if you are on secondary bushings looking at high side bushings.) It seems that ANSI 57.12.10 may be defining it in a different way, but Fig 3 is very clear for H1 position. You have a point that R1....R6 are not per Std.
This transformer is Rectifier Transformer, and now I am not sure how R1...R6 orientation is, wrt high side. If you see the nameplate dwg, H1 and R1 are shown diagonally opposite. But nameplate may not represent physical layout.
If anyone out there who has dealt with rectifier Transformer, will be better able to assist with both HT and LT bushings orientation.

Thermionic1, This transformer has Off-load tap changer which can be operated by rotating a big knob located in the center of the top of the transformer. Thanks.

 

[jghrist]

My bad. This is what prc said. I misread the direction of looking.

 

[prc]

If you want to place LV terminals on the short side of the transformer, Terminals X1,X2, X3 are moved clockwise or anticlockwise. The rating plate is normally placed near the driving handle of the tap-changer. The Rating plate also will have a sketch, similar to fig 3 of C57.12.10

 

[RRaghunath]

This notation seems different from that of IEC where standing in front of transformer facing HV terminals Left to Right is H1 to H3.
PRC Sir may throw more light on this. Thanks.

 

[Pdave6]

Thank you all who have taken time to respond. This transformer was made by GE in USA hence it should be ANSI std. I have not read Ansi C57.12.10. I have no knowledge of IEC std either.
As far as Off-Load tap changer is concerned, one has to physically climb on top of this transformer and rotate the knob which is located in the exact center of the top plate.
I see that 490 volt secondary bushings, R1...R6 may not match a standard, but probably will have some accepted industrial practice. I will try to contact one transformer manufacturer, if he can shed some light on this old GE unit. I will share if I get any more info.
Thanks.

 

[wroggent]

From C57.18.10-2021 IEEE Standard Practices and Requirements for Semiconductor Power Rectifier Transformers

From IEEE 1653.1-2016 IEEE Standard for Traction Power Rectifier Transformers for Substation Applications up to 1500 V DC Nominal Output

From IEEE 1653.2-2020 IEEE Standard for Uncontrolled Traction Power Rectifiers for Substation Applications up to 1500 V DC Nominal Output