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  1. tgott

    Small Generation

    Talk to the utility about size as well as other interconnection issues. You don't just "connect" to the grid; many issues have to be considered. You might also consider there must have been some reason the utility didn't put the generator in themselves!
  2. tgott

    copper bus bar temperature rise

    jbartos: Thanks for the Google search.
  3. tgott

    ONAN/ONAN/ONAN?

    BLadewig: I agree that does seem strange, especially when it is a single MVA rating. Perhaps there is a temperature requirement, ie. 55C / 65C, but I've never seen it written that way. I would suggest its either a typo, its an error from putting a spec together from multiple spec's, or the guy...
  4. tgott

    CT choice for transformer feeder

    CT ratios are selected by the current they are expected to see at the point of installation; this is regardless of where a fault is located. Using your numbers: I = 20MVA/ ((sqrt 3) * 11kV) = 1049.7 A. So a CTR = 1200/5 is reasonable for the 11 kV side of the transformer. CTs installed on the 66...
  5. tgott

    PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS

    Since both transformers have the same rating, to figure out the distribution between the two, simply divide the impedance of the other by their sum (.0597 + .061 = .1207). The transformer with 5.97% impedance will carry .061/.1207 = 50.538% of the load; the 6.1% transformer will carry...
  6. tgott

    Step-type Voltage Regulator Impedance

    Also from Westinghouse T&D Reference Book Chapter 5, page 117. The ratio between winding kva (Up or Us) and circuit kva (Uc) is, Up/Uc = Ea x Ip/Ea x Ia = Ip/ (N/N-1)Ip = N-1/N For example, an autotransformer rated 1000 kva, with a circuit voltage ratio of 22 kv to 33 kv (N = 33/22 = 1.5)...
  7. tgott

    Step-type Voltage Regulator Impedance

    From Westinghouse T&D Reference Book, Chapter 11, page 395 TABLE 13 - Impedance of Feeder Regulators - Percent On Circuit KVA Base - Plus or Minus 10 Percent Regulation Max. Min. Neutral Pos. Induction Single-phase..................... 2.5...
  8. tgott

    Earth grid construction

    For foundations our practice is to bond the anchor bolts to the rebar and then to the ground grid. I don't know of any standard but experience has shown that when we don't do this, our foundations sometimes get broken after a lighting stike due to the current coming down the metal structure to...
  9. tgott

    Temperature rise calculations for generators

    light bulb! I think I get it now. No offense taken at all electricpete. Thanks for your reply. Think I'll stick to transmission planning though. :-)
  10. tgott

    Temperature rise calculations for generators

    As I originally stated, I am no expert, but now you've got my interest and I'd like to understand. I guess I don't even understand the question correctly. Whatever allowable temperature rise numbers you use, the underlying fact is that class F machines have a larger allowable temperature rise...
  11. tgott

    line surge arrester

    http://www.hubbellpowersystems.com/powertest/tips_news/pdfs_best/EU1202-H.pdf
  12. tgott

    Temperature rise calculations for generators

    DISCLAIMER: I am by no means an expert on this and am only posting this for your consideration. It may be totally off base. Now, I'm not sure I understand your question, but for a class F totally enclosed, nonventilated motor/gen. the allowable temperature rise is 110 degrees Celcius. For a...
  13. tgott

    Very Brief Overview of Symmetrical Components (positive, negative, & zero sequence)

    Reference Protective Relaying Principles and Applications by J. Lewis Blackburn. Considering a three-phase system, symmetrical components (positive sequence, negative sequence, and zero sequence) allow one to analyze power system operation during unbalanced conditions such as those caused by...
  14. tgott

    Positive Sequence Impedance vs. Negative Sequence Impedance Concept

    Yes you can. In our transformer specifications we have two statements regarding the symmetrical components. Under the TESTS heading: Impedance and load loss at rated current on the rated voltage connection and on the tap extremes. Test sheet impedance values shall include both the positive...
  15. tgott

    What's the difference between live tank and dead tank circuit breakers?

    With live tank circuit breakers, the enclosure that houses the contacts is energized, ie. "live". Dead tank circuit breaker's contact enclosures are not energized and are connected to the ground grid. Live tank breakers are usually less expensive but you have to have separate current...
  16. tgott

    Positive Sequence Impedance vs. Negative Sequence Impedance Concept

    Eddypach- not an easy thing to do via the forum, but I'll give it a shot. Considering a three-phase system, symmetrical components (positive sequence, negative sequence, and zero sequence) allow one to analyze power system operation during unbalanced conditions such as those caused by faults...
  17. tgott

    Web site Information on Circuit Breaker

    You didn't say whether you were looking for power circuit breakers or household breakers. For household http://www.howstuffworks.com/circuit-breaker2.htm. Also see http://www.tpub.com/neets/book3/8i.htm...
  18. tgott

    Autotransformer 220/115/38.5kV + compensation winding

    Yes you should be able to purchase a 4-winding transformer. We spec'ed one last year to serve as a start up transformer and received bids from Waukesha Electric and ABB Power T&D. Following is how we specified. Primary Voltage: 161 kV RMS, wye connected to a 161 kV grounded wye system. The...
  19. tgott

    Transformer Protection

    You might try http://www.sandc.com/products/smd_od/smd_od.asp
  20. tgott

    physical explanation of induction disk relay

    I'm sure that you've probably read many text book explanations, but I can only offer another. GE's Art & Science of Protective Relaying manual has a section titled "The Production of Actuating Force" http://www.geindustrial.com/industrialsystems/pm/notes/artsci/art02.pdf (page 10 of 22).

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