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  1. Latango

    Txf DGA sampling question

    Yeah, that was the vendor's procedure we have been using, but the oil processing lab, as well as other individuals in the organisation, recommend sealing the glass bottle/plastic lid up with zero air gap. Looks like there isn't an international standard on this sort of thing. Thanks for the input.
  2. Latango

    Txf DGA sampling question

    There's been a question raised about DGA sampling methods in our organization. The procedure calls for filling both a syringe and a 0.5L glass bottle. The question is, how much airspace should be left in the top of the 0.5L bottle to allow for expansion? The opinions range from "a little bit" to...
  3. Latango

    Why transformer insulation resistance decrease when filled with insulating oil?

    I'm going to hazard a guess here and say that when a liquid is acting as the dielectric, there is a massive difference in the number of atoms sitting between conductors and earth than when there's a gas there, thus more paths for energy to move. Also, if it wasn't oil they filled it with, and...
  4. Latango

    Grid scale BESS inverter question

    In general I am one of the guys building and testing that sort of gear, not designing them. This post (using an old diesel generator in place of a cap bank / shunt reactor setup / however else line reactance is combatted) certainly highlights (to me anyway) the difference in knowledge levels...
  5. Latango

    Grid scale BESS inverter question

    davidbeach: I'm not on the commissioning team, only construction, thankfully :) PE have their own techs doing the hard stuff, so I imagine they're doing the right thing. waross: Perfect, that's what I thought might have been the case, but lacked the language and understanding to express it...
  6. Latango

    Grid scale BESS inverter question

    I'm sure that the software would make them all work hand in hand, unless there's a fault on a battery or something. The question that I can't find the answer to is HOW does the inverter change the power flow? Is it as simple as voltage higher than grid = power flows out (discharge into the...
  7. Latango

    Grid scale BESS inverter question

    I have tried to find this information online, but I can't seem to find a difinitive answer. In our country we are starting to install quite a few large battery systems to try to cut back on peaker plants, along with many others I assume. I am curious though, at the 100MW+ size installations...
  8. Latango

    Reduction in tan Delta as well as insulation resistance

    Is there any cracks anywhere that might let a bit of moisture in? Dissipation and IR both drop from water ingress, especially at that level of drop.
  9. Latango

    So im working on some 500Kva Xfmrs

    Standard volume for a DGA sample is usually 0.5L. Maybe the client misread the email from his engineer, or the engineer missed the decimal point? Given that the average 500kVA probably has between 400 and 600 L of oil in it, for a piece of equipment with a 20+yr lifespan and a yearly DGA test...
  10. Latango

    High current (6kA) LV s/b question

    ScottyUK: Depending on the c/b it wouldn't be all that difficult really, at that size the few that I have seen have 2 poles per phase, with around 8"ish of width to bolt bar on. Would be a little bit tight, but physically it would be doable with the right tags bolted onto the c/b chassis...
  11. Latango

    High current (6kA) LV s/b question

    If I wanted to run 3 + (1 backup) 1MW 415V generators into a single output, I would expect to have 4 2000A c/b's bussed using copper bar to a single 6300A circuit breaker that would provide the feed out (with OCR's set to correct levels obviously). Even if it was aligned with the 6300A breaker...
  12. Latango

    Transformer de-rating for high ambient temps, which ANSI C57 standard?

    Exactly what I was after, prc. Thanks a lot for that, now to see if I can buy a pdf online somewhere. Cheers, Mat
  13. Latango

    Transformer de-rating for high ambient temps, which ANSI C57 standard?

    Have done quite a few different searches here, and can't pin down which standard I need to get. I cannot find, in Australia, a standard that guides de-rating factors for higher-than-nameplate ambient temps. That is, if I have a 60 - 65 transformer (oil - winding), that is designed for 40 degree...
  14. Latango

    Earthing Transformer (zigzag) Hi-pot Testing questing

    Just a quick question, had a search through and couldn't find an answer: By IEC60076, when doing a separate source voltage withstand test on a transformer, all terminals of the winding under test must be connected together, and all other windings / metal parts, etc have to be connected to...
  15. Latango

    DOL starting motor, 2 dif sized txf's

    Yeah to be honest I don't HAVE any more information, only that the generator was tripping its circuit breaker on o/c while DOL'ing the fan while hooked up to a 1500kVA transformer, but not when hooked up to a 500kVA transformer. There is no fault on the 1500kVA, no fault gases in the oil. The...
  16. Latango

    DOL starting motor, 2 dif sized txf's

    Quick question: If you use a generator (say 750kVA) as a power supply, stepping up through a 500kVA transformer with around 5% impedance, then try to DOL start a 180kW SC motor hooked up to a fan. Will the generator see a significantly lower startup current than if a 1500kVA 5% impedance...
  17. Latango

    Rubber degradation in different mineral oils

    The locally available Flourinert has a boil point of 56 degrees. Without actually building the tank and running an experiment or 2, I'm not sure how the heat dissipation will go, thus Tmax (I'm sure it's calculable but there would be a lot of variables, and I'd only have to be wrong a bit to...
  18. Latango

    Rubber degradation in different mineral oils

    To be honest I DID look at Flourinert, but it would mean a hermetically sealed case, which is difficult with all the multicore cables that need to come out, and at $840 per US gallon here in Australia, it would be cheaper to replace the pc every year and use plain old mineral oil.
  19. Latango

    Rubber degradation in different mineral oils

    Ports: Apparently some people use oil baths for temporary condensation prevention during dry ice / lN2 cooling of components, but that's obviously not long term. Latexman, thanks for that list. I have a few k-litres of silicone fluid here I didn't even think of - providing it's the same stuff...
  20. Latango

    Rubber degradation in different mineral oils

    Mike, Ports394 summed it up quite well. Fun, and heat dissipation in a liquid is far more effective than in air. Quark, Teflon and Viton would be great to make capacitors out of, however I'm not making the capacitors. They are already made. I was just wondering if the chemical world knew of a...

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