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Hi The angles will not be like a balanced three phase system, they will we 180 degrees phase shifted. If you look at the circuit provided the voltages across winding B (ZB) and winding C (ZC) will be as stated earlier. Consider that the winding impedances are equal (1 pu), then you get by...

Hi As Waross pointed out, it is due to polarity. See image below.

@Waross I have made a circuit diagram with phase loss on A which provides the following conditions for Y-side; UA-n = 0 V UB-n = 0.5*UBC UC-n = -0.5*UBC Shouldn't the voltages on the y-side be the same i.e.; Ua-n = 0 V Ub-n = 0.5*Ubc Uc-n = -0.5*Ubc

Hi all For a Y-y transformer ungrounded neutral, what will be the secondary and the primary voltages if phase A in primary is open?

Hi I found the answer. The material temperature correction factor is the same as the temperature coefficient as follows: 𝛼 = 1/(235+20) = 0.003937

Hi all, In the IEC standards for transformer and motors the following formula is provided for calculating the resistance at temperature Θ2: R2/R1 = (Θ2 + 235) / (Θ1 + 235) 235 = copper In University I learned the following equation: R2/R1 = (1 + 𝛼(Θ2-Θ1) What is the difference?

Hi Thanks a lot for your responses. I still dont understand table A.1. In the formula for Xi,k, the LN function is LN(di+1,k/di,k), how can i=1, k=1 be equal to R2R1 ie. 1000 and not 12.73? Thanks

Hi I am struggling to calculate the impedances in Example 1, IEC 60287-1-3:2002 Annex A. Anyone who knows how the reactances are calculated? Thanks!

Hi Tofu I have also asked the same question in this thread: https://www.eng-tips.com/viewthread.cfm?qid=438149. I also asked how to calculate Utp value at 0.05 s. I got the following reply from Erdep: TIME OF FAULT : 0.05 HF : 1. BF : 0.75 WEIGTH : 1. TOTAL ADDITIONAL RESISTANCE : 0. BODY...

Hi Thanks for Your post. It clears up a lot! Im trying to create the table below from your previous post in the program. I assume I have to change some data in the SAMPLE.dat file then run erdep 2? Correct? 1 0.05 712.8433 900.0000 716.0000 2 0.10 610.6242 750.0000 654.0000 3 0.20...

Thanks Erdep How did you calculate the different Z(Ut) by the way? In EN50522 only 775 V for the highest touch voltage is stated, while you have calculated different values depending on the different circuit configurations. I think you can attach the programs to this thread.

Thanks Erdep. This is interesting! How do you calculate the average of 713 V? Im calculating as follows which may be incorrect: 554 + 658 + 418 + 1744*0,7 / (1+1+1+0,7) = 2851 / 3,7 = 770 V. What am I doing wrong here?

Thanks cuky2000, but this does not explain how to derive the values given in table B.3 in EN 50522. However the standard gives some hint on how to derive the curves given the formula in Annex A and values for body impedance and body current given in annex B. The curve in figure 4 in the...

Hi How is for example 716 V been calculated? Can you show this?

Hi Referring to thread238-305712. Im trying to derive the permissable touch voltage curves in standard EN50522 without any success. Can someone please share how to derive these curves? An ExCeL worksheet will be appreciated:) Many Thanks

Hi In IEC 60076-8 it is stated that YNd and Yzn earthing transformers has the same functionality. I understand the broken delta solution (YNd), but I am struggling with understanding the Yzn solution. For instance, if you have a 11 kV delta connected system and introduce a 11/0.69 kV Yzn...