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  1. System Protection

    Power Transformer Rating

    Yes, but I would also look into transformer operating temperature vs longevity. Could be more economical to run a larger transformer at less than max capacity vs a running a smaller one at 100% rating. There are papers on sizing transformers (economically). Not sure if there is one specific...
  2. System Protection

    Transformer test report - zero sequence values

    Is that MVA for a 3 phase transformer? Or do you have three single phase transformers?
  3. System Protection

    Dead tank high voltage circuit breakers in Europe

    I imagine there is an interconnection agreement between the TSO and customer. The requirements should be laid out there. Not sure about any other legal requirements in Europe though or the legal authority of the TSO to impose restrictions on the breaker construction. I have not done any work...
  4. System Protection

    Electrical power system protection - book

    https://www.eng-tips.com/forums/238/faqs/1287
  5. System Protection

    LED Light Degradation

    It's an unfortunate problem. I replaced some LED bulbs that were 3 or 4 years old (intermittent use) with the exact same bulb and the difference in light output was huge.
  6. System Protection

    Spain and Portugal power grid collapse

    I imagine it will be a long while before we have a conclusive analysis. It's outside my realm but if I had to guess I'd say it will have to do with the "ride through performance" of the inverters. Perhaps incorrect (or insufficient) Inverter settings.
  7. System Protection

    Digikey Alternatives

    Mouser is another big supplier. What types of electronic components are you looking for?
  8. System Protection

    Questions regarding transformer's percent impedance in other than nominal voltages

    I should clarify my comments as the transformers I used to test were autos. I could get a decently accurate reading on a short circuit impedance test with very little voltage. Just using 120VAC and a variac. The excitation requirements are less than a regular transformer though. There was...
  9. System Protection

    Questions regarding transformer's percent impedance in other than nominal voltages

    You should be able to convert from PU to actual impedance (ohms) and calculate from there. It's been a long time since I've tested a transformer, but I'd often have to do that in reverse. Start with an actual impedance and convert to PU to check against the nameplate.
  10. System Protection

    Looking for the name of a material

    Monarch textiles sells what they call oil absorbent felt. Might be close to what you're looking for.
  11. System Protection

    Transmission ground distance relaying with distribution underbuild

    Any chance this started as a distribution fault? Could explain the prefault. I remember seeing some strange prefault waveforms and it was due to the underbuilt distribution faulting first. Or perhaps evolving into a transmission to distribution fault?
  12. System Protection

    Transmission ground distance relaying with distribution underbuild

    Another fault location method is to compare the ratio of 3I0 current from each end of the line. That should help account for fault resistance. You would use Synchrowave to get the 3I0 current from each end. Divide one end by the other. Then run intermittent faults in your fault sim program...
  13. System Protection

    Transmission ground distance relaying with distribution underbuild

    How are you finding the best fit with your fault program? Could the fault resistance be the reason your Z0 seems low?
  14. System Protection

    Transmission ground distance relaying with distribution underbuild

    Typical would be 85% reach for Phase distance and 70% reach for Ground distance for Z1.
  15. System Protection

    Transmission ground distance relaying with distribution underbuild

    I model it all in the line constants program that I use as its not much more effort to add the underbuild. But I don't input the mutual impedance between transmission conductors and underbuild into my fault sim program as the distribution system is not modeled. Definitely would recommend...
  16. System Protection

    Semi Hauling Excavator Hits Bridge over I-10 in New Mexico

    I checked a random spot on I10 on Street View and it showed 75MPH without a separate speed for trucks.
  17. System Protection

    Wait to reenergize following lightning?

    Single Phase Auto Reclosing I don't think its that common below 500kV. At least that I've seen in the USA.
  18. System Protection

    Things you love/hate with mathcad

    I'll add another MC Prime annoyance. If you are paging up and your cursor lands in a text box you will enter in it and will have to click outside of the box to continue paging up.
  19. System Protection

    Wait to reenergize following lightning?

    This makes sense. Maybe their policy got lost in translation somewhere.
  20. System Protection

    Wait to reenergize following lightning?

    Nope. What would they do if a significant portion of their lines got hit with lightning? Just leave half their lines out of service? Its normal to go inspect a line that trips to lockout before attempting to re-energize but I've never seen one left de-energized after the problem was found/fixed.

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