Results 1 to 4 of 4

Thread: Excessive voltage loss under load results

  1. #1
    Site Caretaker Dave A's Avatar
    Join Date
    May 2006
    Location
    Durban, South Africa
    Posts
    22,648
    Thanks
    3,304
    Thanked 2,676 Times in 2,257 Posts
    Blog Entries
    12

    Excessive voltage loss under load results

    We're finding quite a few properties with excessive voltage loss under load problems.

    Here's an example:
    Voltage no load: 231.2 V
    Voltage test load (16A): 223.8 V

    And that's tested at the meter.

    For the record:
    Neutral voltage: 0.86 v
    Loop test: 0.5 ohms
    PSC: 0.5 kA
    Main supply limited to 60 A

    Anyone else having problems like this?

  2. #2
    Bronze Member
    Join Date
    Mar 2012
    Location
    Account_Deleted
    Posts
    165
    Thanks
    122
    Thanked 23 Times in 18 Posts
    Hi Dave i might be wrong but if Vdrop (V) = Iwire (A) × Rwire (Ω) = Iwire (A) × (2 × L(m) × Rwire (Ω/km) / 1000)) and since all remains constant and you can proof it eg the 16A, the length of the wire, the only variable would be the resistance of the wire. If the resistance of the wire increases your voltdrop will increase. I have come across total breakdown of conductivity of copper and Al wire.

    ps have you tried different brand meters?

    (8.7.5 Earth fault loop impedance at the main switch
    8.7.5.1 At the main switch, the impedance shall be such that an earth
    fault current double the rated current (or higher) of the main protective
    device automatically disconnects the supply to the installation.)

    Your voltdrop under load is <5% (3%) and your loop test is more than double the rated current for the main protective device.
    Last edited by ACEsterhuizen; 17-Dec-14 at 01:23 PM. Reason: mistake

  3. #3
    Diamond Member AndyD's Avatar
    Join Date
    Jan 2010
    Location
    Cape Town
    Posts
    4,923
    Thanks
    576
    Thanked 934 Times in 755 Posts
    It could be a poor termination somewhere in the supply cabinet on the street. There could be a bottleneck, it wouldn't be the first time the council use a piece of 6mm wire as a jumper somewhere on a 60A supply. Might be that the council/Eskom HV transformer is a long run from the property. Either way if your tests were done at the meter I'd give the results to the homeowner and get them to log a fault of low voltage with the council/Eskom.
    _______________________________________________

    _______________________________________________

  4. #4
    Site Caretaker Dave A's Avatar
    Join Date
    May 2006
    Location
    Durban, South Africa
    Posts
    22,648
    Thanks
    3,304
    Thanked 2,676 Times in 2,257 Posts
    Blog Entries
    12
    Quote Originally Posted by ACEsterhuizen View Post
    Your voltdrop under load is <5% (3%)
    For the test load (16A), true. But with the maximum load (60A) the volt loss would be 27.75 V, or 12% in the above case

    Quote Originally Posted by ACEsterhuizen View Post
    ps have you tried different brand meters?
    I'm seriously considering going down that route. We have two testers which we test against each other from time to time, but unfortunately both the same model. Most of the time the readings we are getting are well within spec though, so I'm not sure it's the meter.

    I probably should point out that we test at the main switch first. It's only when we pick up problems that we then test at the meter to identify whether it's the municipal supply or the consumer's main feeder cable. So by the time we start getting concerned about the quality of the municipal supply, we're already up to two tests.

    What's really starting to concern me is we're finding it more and more often of late.

Similar Threads

  1. [Article] 2011 Business Data Loss Survey results
    By cibecs in forum Technology Forum
    Replies: 4
    Last Post: 24-Sep-11, 07:35 AM
  2. LOSS,HELP or EVEN
    By IMGREG in forum General Business Forum
    Replies: 7
    Last Post: 28-Jul-10, 12:38 PM
  3. Difference between: Power factor correction, Voltage regulation and Voltage stabisizi
    By BigRed in forum Electrical Contracting Industry Forum
    Replies: 8
    Last Post: 08-Feb-10, 09:29 PM
  4. Google still gives best results
    By Dave A in forum Technology Forum
    Replies: 4
    Last Post: 28-Aug-09, 02:50 PM

Did you like this article? Share it with your favourite social network.

Did you like this article? Share it with your favourite social network.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •