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Thread: Electrical supply voltage

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    Electrical supply voltage

    I have not participated on this forum before and decided to do so having read some of the q&a's which I found most helpful.

    Over the last 2 weeks I noticed some of my GU10 50w's flickering, fluorescents also flickering and last night a CFL on a plug point. I spent time trying to isolate the cause as I normally suspect dimmers....I could not find the fault but noticed that one of my phases (checked unloaded) has a reading of 209v whereas the other two 236v. It is really the CFL on the plug point flickering that made me think that it is not a demand side problem. I then swapped phases and the flickering is gone. Could it be that it is a corroded / burnt etc breaker on the pole maybe? Thanks, would like to know your thoughts.

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    Could be a number of causes and corroded / burnt connection is one of them.
    Also could be that the phase is overloaded from the supply side and often it is the red phase which from general habit gets loaded first.

    Phone the supply authority and let them come and check.

    SANS 10142 allows for the voltage to be as low as 207 V as an incoming supply and then you are allowed another 5% drop. So 197 V could be acceptable according to the code - Some lamps/LED drivers are coming in rated at 220v to 240v and as soon as the voltage comes close to the parameters they start failing


    5.4.2 Voltage

    The equipment shall be suitable for operation on the maximum steady
    (r.m.s.) voltage and overvoltage to which it is likely to be subjected.
    Equipment shall be rated in accordance with the intended application for use
    on one of the following voltages used in South Africa:
    a) A.C. circuits:
    1) standard voltages of
    i) 230 V single-phase
    ii) 230/400 V three-phase four-wire, and
    a tolerance of ± 10 % on these voltages.
    NOTE For certain equipment it may be necessary to consider the lowest voltage
    that is likely to occur.

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    Weimaraner (18-Jul-19)

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    Thanks for the reply.

    I traced the fault to one of my phases (blue) and concluded that it was a supply side problem after I swapped phases on my DB. I swopped it back as was before (flickering occurred) and I logged the fault with Jhb City Power on the 15th, they came the afternoon, told my wife it was a loose connection in the boundary box on the supply side and the problem went away. Yesterday I lost another phase (white/yellow) and I decided to have a look in the boundary box. City Power lied.....all they did was removed the blue phase and bridged white/yellow onto blue with a thin wire. I have a 3x100amp installation so we all know that 16mm2 wire is what should be used. In addition the demand side wire at the breaker was loose and I noticed oil coming from the breaker and the screw connection looked a little worse for wear. I again logged a dangerous fault call (this is a dangerous situation in contravention of SANS) and at 1am this morning City Power was at my gate. They saw the mess, agreed that it is unacceptable and replaced the box breaker and white/yellow phase now working. Blue still not working so up the pole they went - fuse faulty - new breaker and problem sorted. They only had 80a breakers so bringing 100a this afternoon. See below the photos of the mess. What is the best way to bring the non conformance to the attention of the authorities?Click image for larger version. 

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    The easiest and fastest method with the best results ,will be to talk to the brick wall in front of you - More than likely the wall will listen with a sympathetic ear.

    Jokes aside - I would think that you did log a dangerous fault call and the fact that they responded quickly would hopefully mean that somebody would have noticed and escalated the problem internally

    If I was wanting to take it further , I would first take blood pressure tablets and then try phoning through to complaints and see if that gets anywhere.

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    Weimaraner (18-Jul-19)

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    Quote Originally Posted by Weimaraner View Post
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    I confess - I'm pretty gobsmacked by that.

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    WOW! that is unacceptable. hopefully you didnt have any 3 phase equipment running...
    by the way 80 amp breakers would be the correct size not 100 amp.

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    I do not have the energy to deal with City Power, you are right, my blood pressure will rise.
    In 2006 I specifically upgraded the breakers to 100amps but now I am wondering what the pole breaker ratings are? It has never kicked so so far so good
    Thanks for all the help and responses.

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