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Recent content by Gauss2k

  1. Gauss2k

    Transformer inrush vs short-circuit current

    I was reading an interesting document made by S&C about the calculation of a transformer inrush current based on the impedance and the short-circuit available at the primary side of the transformer: http://www.sandc.com/webzine/2003/012003_1.asp We usually use a 8 to 12x nominal value for 0.1s...
  2. Gauss2k

    Harmonic filter

    Thank you for your answers! Yes, indeed, for the capacitor. I also thought about that later yesterday, it was obvious after all! As for the measured value for the reactor, 66mH instead of the 115mH mentioned by the manufacturer, I think it is because the value measured on a single phase does...
  3. Gauss2k

    Harmonic filter

    I am currently reading a report talking about the test and sizing of an harmonic filter. I have a couple of questions about how they managed to get their results. Here we go. The filter is made of one 3-phase reactor, with a value on the plate of 115 uH. In series with this reactor are four...
  4. Gauss2k

    Current decrement data for a turbo-generator

    I am currently working on the coordination study of a factory's emergency network. They have 2 500kW generators and 1 MW turbo-generator. I was able to get all the information I need about the 2 generators as they are only a few years old. But unfortunately, the turbo-generator was made in the...
  5. Gauss2k

    T-T connected transformers

    I was looking for informations about T-T connected transformers because I saw a couple of them in the last months. I found this thread via google where it was briefly discussed: thread238-151261 Some manufacturers like "Marcus Transformers" (http://www.marcustransformer.com), also found with...
  6. Gauss2k

    Medium to high voltage measurements

    Of course, we use the cts and vts when available, which is most of the time. I must say I don't really enjoy the idea of taking measurements on live medium voltage cables. Even if every and all precautions are taken, there is still a higher risk than working on cts and vts. But we have...
  7. Gauss2k

    Medium to high voltage measurements

    We would like to take measurements on a 25kV transmission line (voltage and current). Other than installing permanent current and voltage transformers, is there something else we can use to record those values over a short period of time? A few months ago, I remember receiving a publicity...
  8. Gauss2k

    Water content in oil

    We also already do that, we clean the jar and syringe with the transformer's oil three times, after removing the 1-2 liters ;) We take a lot of precautions to avoid contamination when taking the samples. That's why I wondered if the higher result *could* be real in some cases..
  9. Gauss2k

    Water content in oil

    We regularely take oil samples from our clients transformers in order to analyse their dissolved gas content and oil properties. Sometimes (and it happens a couple of times in the last few months), we see a sudden change in water content (for example from 10 ppm to about 50 ppm a year later)...
  10. Gauss2k

    Current transformer saturation

    I was looking for the book dpc talked about on amazon.com, Protective Relaying (Power Engineering, 5) by J. Lewis Blackburn: http://www.amazon.com/Protective-Relaying-Power-Engineering-5/dp/0824799186/sr=8-1/qid=1158934286/ref=pd_bbs_1/002-1679553-7031209?ie=UTF8&s=books I saw another...
  11. Gauss2k

    Current transformer saturation

    Thanks for all the valuable information, i will study it very thoroughly. I will try to find more information about the CT type in order to predict what would happen during a 6kA fault.
  12. Gauss2k

    Current transformer saturation

    I have a question about current transformers saturation. Here's the situation. The building has a medium voltage breaker with its protection relays, on the primary side of its main transformer. The current transformers used by the relay have a ratio of 50:5A. The maximum short-circuit current...
  13. Gauss2k

    PCB transformers standards

    rbulsara: The tests were done as an annual inspection and verification. Both transformers were online before the tests and they are online as we speak. The units are about 30 years old and are delta-wye. We have no history about earlier testing. Unclebob: MB told me the same thing, but there...
  14. Gauss2k

    PCB transformers standards

    rbulsara: the dielectric strength was about 33 to 35 kV (standard test) Zogzog: The voltage was applyed for 1 minute. I know the voltage is not high, but that doesn't explain why we got those results. The polarization index was not calculated. By the way, all cables were disconnected during...
  15. Gauss2k

    PCB transformers standards

    Hello everyone, We just tested 2 PCB transformers: ratio, winding resistance, PCB dielectric breakdown and insulation test (megger @ 1kV). All the tests gave good results on both transformers, but the insulation tests we're pretty low on -both- transformers primary side (about 8 to 9 MegOhm...
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