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Recent content by ters

  1. ters

    Hoist motor load test failure

    You actually may never solve your problems if the machine is designed for 50Hz. Whatever you do along the lines other posters proposed, all your motors will still run 20% faster at 60Hz. So if machine design is such that some of its rotating functions cannot be accelerated for 20%, then there is...
  2. ters

    Room Ventilation for SF6 gear

    I have worked on various MV and HV GIS, and while there is almost always detection and ventilation for HV gears, I don't remember seeing any of that for MV installations. For example, some GE wind turbines are supplied with a Schneider SF6 gear inside, up to 38kV, it is located inside a small...
  3. ters

    load bank for testing 5000 kVA generator

    My initial impression was that you wanted to have a permantly installed load bank for regular standby diesel testing, which is typically the case for installations where the grid feeds the loads while an emergency stanby diesel is used for critical loads only when the grid is down. As it may...
  4. ters

    load bank for testing 5000 kVA generator

    On a previous project, a 3MW diesel operating at 13.8kV used a 2MW LV load bank made by Avtron (USA), a permanent connection via a 2MVA step down transformer. But their web site indicated that they also make MV load banks up to 15kV and 7MW...
  5. ters

    Arc flash hazard in outdoor 230kV substation

    Thanks you very much gents. Looks like there is significant confusion about arc flash out there and some more room for separating myths from the reality, although I’m obviously not an expect for arc flash studies and making comments based on common sense and general electrical knowledge only...
  6. ters

    Arc flash hazard in outdoor 230kV substation

    What would be a practical approach for assessing actual arc flash hazard risk level when one is just walking inside a 230kV switchyard (N. American case)? It does not seem to me that empirical formulas in NFPA 70E and IEEE 1584 would be adequate to use since, given the typical fault level of say...
  7. ters

    Wind farm step-up transformers - excessive gas problem

    Prc, re your star/delta question, for all wind installations I have seen so far, the star was on the low side which connects to the converter.
  8. ters

    Wind farm step-up transformers - excessive gas problem

    Prc, thank you for you posts again. mopractice, it is good to know that I’m not suffering alone :). Thank you really very much for your post. Very informative. If I understand your post well, you had two project phases, so transformers were not made at the same time, maybe one year apart, but...
  9. ters

    Wind farm step-up transformers - excessive gas problem

    Thank you all for replies. Jebb, yes we did suggest trying different oil in one of the units but it is not up to the owner to decided. Prc, I just googled a specific sentence from that document and found it also available as public here...
  10. ters

    Wind farm step-up transformers - excessive gas problem

    For simplicity reasons I described one facility with 5 units, but there are actually two similar facilitates at the same location, connecting to the same utility line (separate connections) experiencing very similar problem. In summary, there are nine 2.5MVA transformer all gassing more than...
  11. ters

    Wind farm step-up transformers - excessive gas problem

    In this particular case, the hypothesis abut collector resonance was considered (and partly modeled) but it was too fuzzy to find any sort of logical explanation for it given the diversity of actual oil tests: There is a turbine which is just 200m from the substation, it has its own feeder...
  12. ters

    Small Generators - Large Transformer Inrush

    I have recently been involved in the commissioning of a 3MW diesel generator which we tested un inrush using a 2MVA transformer (a larger one was not available). Your case will be more challenging than this, but in our case we had no issues except we had problems with differential protection -...
  13. ters

    Small Generators - Large Transformer Inrush

    Would a shorter version of this question be: There is no grid. Two 2.5MW 480V generators connect to a 12kV bus via step-up transformers and can be synchronized to each other. The 12kV bus feeds ten 1000kVA transformers which for some reason cannot be staggered but have to be energized all at...
  14. ters

    Wind farm step-up transformers - excessive gas problem

    We are aware of other wind farms experiencing this problem but looks like the extent varies widely. In some other cases the gassing level seems to be increased but not alarming. Looks like there is no clear scientific explanation as why this is happening and various theories are floating around...
  15. ters

    Wind farm step-up transformers - excessive gas problem

    Fellows, I would like to post a follow up on this. I came across a presentation done by a reputable engineer, IEEE Fellow and member of IEEE's Transformer Committee , etc, which unfortunately I cannot publish here due to that thing: “all rights reserved” , but in essence the conclusion is...
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