Recent content by allmend

Hi skogsgurra, I answered your posting from Mar 2, 2004, in this posting you didn’t mention the non-existent neutral. I don’t have any doubt that all participants of the discussion are experts in power supply. The only problem we have in this discussion is that nobody reads the postings of...

„A wye/wye transformer has a high impedance to all zero-sequence currents“ --- skogsgurra, What do you mean saying „to all zero-sequence currents“. I guess there is only one zero-sequence current, though there may be many harmonics in the fault current. Only the 3xNx50/60-Hz-impedance is...

Speaking about grounding of star points. Some German utilities are using YY transformers with a D-tertiary winding (for example 110 kV/20 kV), the primary star point is grounded, but not in every substation. You have to reduce the fault current to 10 kA (to reduce the fault voltage on the...

„I answered question number 1. And what I say about distortion is right.“ ----- skogsgurra, I am sorry if I misunderstood you. Though English isn’t my native language I had the impression that Jbarts commented on question Nr. 2. JatTiw wanted to know: “ What are the disadvantages if both...

To Jbarts: „I cannot see any reason why zero-sequence current path should be discontinuous in the grounded Y-Y transformer on the both sides.“ ---- Yes, in the grounded on both sides Y-Y transformer you have a zero sequence current in the primary and secondary winding. But in this case...

JatTiw (Electrical) wrote on Mar 1, 2004 2) What are the disadvantages if both the star points (primary & secondary) are connected to the same grounding grid? jbartos (Electrical) answered on Mar 2, 2004 ///All harmonics will propagate through the transformer, zero-sequence current path...

„All harmonics will propagate through the transformer, zero-sequence current path is continuous through the transformer, one line-to-ground fault will trip the transformer, etc.“ --- Please elaborate, Jbartos. I cannot see any reason why zero-sequence current path should be continuous...

„What are the disadvantages if both the star points (primary & secondary) are connected to the same grounding grid?“ ---- I do not see any disadvantages. If the high voltage and low voltage gear is installed in a common room, you even have to connect your star pints to avoid dangerous voltages...

Our utility uses D/Yn (20 kV/0,4 kV) Transformers for power distribution. The 20-kV-Net (mostly cables) is compensated. The advantage is that you can locate and switch off the earth faults without interruption of the power supply.

Hi to all! I believe that everybody knows the definition of the “effective value of a current”, but the discussion is about the measurement and the calculation of this “effective value”. Mr Ohm discovered his law before the invention of a AC-Generator, but AS-Current can also be used for...

„Therefore, there is the relationships between Iav=0.634 Imax and Irms=0.707 Imax. This has not been properly addressed by most postings above.“ jbartos, We are not talking about sine waves, we are talking about „ugly current“.

skogsgurra, English spelling and beer are really very interesting matters to discuss, but I guess that you are referring to the posting of Scotty, when you talk about a “large beer”. I just typed “bear” instead of “beer”. I couldn’t correct my spelling, because I cannot find in this forum the...

Hi jghrist, I noticed right away that I misspelled “Scotty” and “beer”, but you cannot edit your postings in this forum, can you? Ich wollte keinen Baeren aufbinden! P.S. In Spain you have to say: Una cerveza, por favor :-)

[b]„I can barely ask for a large beer politely in German!“[b] Thanks, Schotty. My English is far from perfect, but I try my best. PS: You do not have to speak German when you ask for a bear in Germany. Every German speaks basic English. ;-)

Hi ScottyUK, Hi Laplacian, I’m German and I work in a Public Utility and my job is power quality maintenance. In Germany they do not use the term RMS, they still say “effective value” (Effektivwert). You cannot neglect the harmonics in a public utility net. If the THD of your voltage is...