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  1. sabrepoint

    Bending of beam subject to offset transverse force

    Sorry if this is too basic but I'm unsure re this and haven't found similar on Web ... Formula to determine moment at R? Thanks from an electrical
  2. sabrepoint

    Overhead SWER Lines

    Thanks Jon After the posting I was surprised to discover so much 19.1 kV SWER in Queensland (and NT too I think). Then I found some in the bottom of NZ as well! So I spent some time talking to Otago Power who were very helpful. Their system is actually 22 kV; some sourced from 11 kV but most...
  3. sabrepoint

    Metal Halide lamp in-rush current

    Ruudites you say! But not Luddites I trust. The guy who gave us the quote is away for a few days but I'll come back after.
  4. sabrepoint

    Metal Halide lamp in-rush current

    Thanks both Well it seems to me there is an in-rush magnetising current decreasing over a few cycles, similar to what is found with transformers. Then will be the much-reduced 'starting' current for a few minutes prior to full output. If this is the case I need to consider whether the volt...
  5. sabrepoint

    Metal Halide lamp in-rush current

    Thanks itsmoked I Googled following up your response (should have done this first!) and have a better understanding now. You're saying there is no large current flow for a few cycles during the magnetising of choke? In a nutshell, I just need to ensure that I can use the operating current in...
  6. sabrepoint

    Overhead SWER Lines

    My thanks to both of you. I have followed some of the suggestions up. Cheers Graeme
  7. sabrepoint

    Metal Halide lamp in-rush current

    Hi I'm no lighting engineer so please bear with me. I need to calculate the cable voltage drop during start and operating conditions of the Ruud CF3499 flood light fitted with 1000 W 240 V MH lamps. I was under the impression that any light fitted with a choke would have a large in-rush...
  8. sabrepoint

    Overhead SWER Lines

    Thanks cuky2000. I'll follow this up. Incidentially the 2nd-to-last line should read "... requirement with 22 kV 3-wire system (12.7 kV to ground)."
  9. sabrepoint

    Overhead SWER Lines

    Hello In New Zealand we have quite a lot of SWER (single-wire earth return) line in various remote areas. In fact I think a NZ power board engineer developed the concept in the 1930s. As far as I know it’s all 11 kV line-to-ground. Under the old regulations such a system was limited to 8 A...
  10. sabrepoint

    Math question - weighted average

    You're right, thanks desertfox!
  11. sabrepoint

    Math question - weighted average

    Hi All Not really electrical engineering, but I'm trying to apply formula to engineering problem ... The following formula determines the Weighted Average Life (Lavg) of a group of power poles ... Lavg = Qconc/Qtot * 60 + (Qtot-Qconc)/Qtot * 45 where Qconc is quantity of concrete poles, Qtot...
  12. sabrepoint

    Bending Moment

    They're both great ... thanks! Actually I had the correct answers as it turned out, but couldn't really explain. Values used were hypothetical ... amongst other things I occasionally survey power lines. The first scenario roughly simulates the transverse wind applied to a wire on a suspension...
  13. sabrepoint

    Working Loads Vs Limit State Loads

    Hello axle Interesting topic, and fills in quite a few gaps for me. I'd be particularly interested in any response regarding your first point "Firstly, are the loadings that were used in a working load design ...". I stand to be corrected, but I think the scheduled Ultimate LS...
  14. sabrepoint

    Bending Moment

    Hi ... sorry this is so simple for you lot but I never did well at mechanics and it was sooo long ago. 1) I know if I plant a 5 meter high post in concrete and apply a 1 kN horizontal force at the pole tip, the pole moment is 5 kNm. That's easy enough, but what if I weld a right-angled fitting...
  15. sabrepoint

    Power line sag/tension calcs

    In case it's unclear, my example values (including my "starting point") are Finals. After fixing my wind load error, my results are each within 1 % of alehman's. And I'm pretty happy with that!
  16. sabrepoint

    Power line sag/tension calcs

    Well, jbartos, not by me. Actually, I'm working in a minimal snow region, where the standard simply states that a 30 mm radial covering of snow at 0.4 SG be provided for. In the example I allowed 12.7 mm radial ice to keep things simple. AS/NZS 4676 standard does not consider other than radial...
  17. sabrepoint

    Power line sag/tension calcs

    Thank you both! Excellent. alehman, your figures especially are very close to mine ... I'd double-counted my drag coeff hence my error during wind. Now reset Cd to 1.0 at 1 kPa and get 20300 N at 15 deg. And it seems I've done the ice part OK too. So I'm rapt with correlation. jghrist, I'll go...
  18. sabrepoint

    Power line sag/tension calcs

    Thanks jghrist You're probably correct, but for our purposes the figures stated will be OK. We have used manufacturers' composite E and coeff data (also scheduled in engineering handbooks) for many years and as far as I know, have never caused a problem. In any case, the Wolf ACSR used is just...
  19. sabrepoint

    Power line sag/tension calcs

    Hi alehman. Looks like just what I need! I'm in New Zealand and haven't managed to find any commonality between any US and NZ conductors [you're in the US?] so I've included parameters. Hope metric OK, but I can convert for you if need be ... WOLF ACSR: A = 195.0319 mm2 Effective Overall Dia...
  20. sabrepoint

    Power line sag/tension calcs

    Hi advidana. I actually have this doc and Bull 1724E-152 which I believe supersedes it in part. As far as I can tell at a glance the basic S/T maths are pretty much the same as that which I've used. My concern is really to see if I've correctly applied the formulae when using ICE (having had...

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