Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. ausgen

    Earthing of Mobile Machine

    mgtrp, I'm not quite following the downstream DB comment. Is this including an outbuilding arrangement? My understanding is that if it's single installation (with no outbuilding) there should only be a single MEN otherwise we'll have parallel return paths. In terms of higher fault level, if...
  2. ausgen

    Underground Cable - any standard for minimum depth

    In Aus, minimum LV depth to top of cable/conduit is: * 500 mm * 300 mm if covered with 75 mm concrete. * 50 mm if chased in rock.
  3. ausgen

    3 or 4 pole breakers at TX and G sides

    I mostly agree, but often have a case in my designs where a smallish gen (500 kvA say) will be connected to a sub-board that might be a 50 m run from the MSB containing the MEN. With typical X0 values, the additional impedance in the fault loop along the earth conductor to the MEN and then back...
  4. ausgen

    3 or 4 pole breakers at TX and G sides

    Most commonly in this part of the world, 3p/3p is used for switching at the board containing the MEN and 3p/4p used at DBs with a remote MEN. 4p/4p configuration remains acceptable under AS/NZS 3000:2007 but is not encouraged to the extent that it was in AS/NZS 3010:2005. It is true that a...
  5. ausgen

    Power Quality Meter Location

    To help with your first question, how valuable it is depends on how critical your loads are and how important it is to understand the details of any supply issues. If you decide that it's important to have some idea of what's going on, your next step is to decide how much info you need. Basic...
  6. ausgen

    Earth Leakage

    Earth leakage through the SMPSs on the office PCs and data centre rack equipment might be a big part of the problem. Along with increaingly leading pf comes the leakage through all these capacitors. If you have small UPS throughout the building these add up to 5 mA each also. In a large...
  7. ausgen

    Ground/Earth Resistance Standard Measurement

    Edison - yes, our NEC equivalent (AS3000) deliberately avoids nominating a resistance value. Although it's geared towards ensuring fault clearance under fully metallic return conditions I would prefer it nominate a value and then for the periodic verfication standard (AS3019) to enforce the...
  8. ausgen

    Underground Fuel Tank for Standby Gensets

    To summarise my local (Aus) requirements, you need the following for USTs at least: -Double walled tank w/ interstitial monitoring. -Double walled pipework (incl. vent, fill, etc) w/ interstitial monitoring on wet legs. -Monitored transition pits where joining with single walled pipe. -All...
  9. ausgen

    Ground/Earth Resistance Standard Measurement

    junmal, Fluke publish a testing guide that includes a section on what a "good" ground resistance value should be. It makes reference to NEC and IEEE recommendations (though I'm unsure if these remain current). http://support.fluke.com/find-sales/Download/Asset/2633834_6115_ENG_A_W.PDF For the...
  10. ausgen

    SWER (Single-Wire Earth Return)

    I'm an end user so aside from the varying volts it appears like any other two wire system. I would have suspected that it would be less than 10 Ohms though. 2000 A on a single return would be interesting - these must be the SWER isolation poles I see with the fencing around the base to stop...
  11. ausgen

    SWER (Single-Wire Earth Return)

    Yes, efficiency loss is a problem although running at HV helps. As davidbeach noted, on a network level, these losses aren't enough to justify the additional 1000's (10s of 1000's in my part of the world) of kms of conductor. Ultimately, the customer bears most of the technical drawback...
  12. ausgen

    Working on Stored Energy devices (UPS)

    Isolation is fairly straight forward as long as you know where the sources (rectifier, bypass, battery, output if paralleling) are switched. ScottyUK mentioned a critical point though, large UPS can carry significant energy in filter caps once isolated so best to isolate then wait a while before...
  13. ausgen

    MOV

    SteveFehr is correct in that there's no substitute for primary and secondary protection in your boards. Best practice these days is for diverters at your MSB and multistage filters at your DBs. I look after a lot of mountaintop sites in high GFD areas so my critical controls items are all 24 V...
  14. ausgen

    Motor Power and Control Wires in Common Conduit

    In Aus, the main issue is seperation of different voltage levels. If your control voltage 24 V ac or dc, the LV in the same "wiring system" can cause an EMC issue.
  15. ausgen

    Generator P/Q diagram

    It's not so much that you'll overload your prime mover, but for (especially for leading loads) you might need to limit the demand to stay within the safe range of the P/Q curve. If we compare supplying 1MVA at unity to 1MVA at 0.9 (leading or lagging), you're actually reducing the load on the...
  16. ausgen

    UPS

    I agree with ESOXmaniac. I have loads of rackmount UPS on site and am forever telling the field crews not to discharge test them by pulling the IEC input connector for exactly those reasons. If you check the equipment manuals, there should be a note along these lines buried somewhere. Further...
  17. ausgen

    Trying to understand short-circuit current rating and kA

    Also, if you're referring specifically to switchgear ratings, there might be more than one "fault" rating. Typically, large LV CBs may offer kA figures for things like Icu (ultimate breaking capacity), Ics (service level rating - usually some derate multiple of Icu) and Icw (withstand rating -...

Part and Inventory Search

Back
Top