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Thread: Voltage between Neutral and Earth - When is it a fault?

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    Diamond Member Justloadit's Avatar
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    Voltage between Neutral and Earth - When is it a fault?

    Having seen many threads in which there are Earth faults created by bad connections such as
    Corroded Earth termination
    Loose Earth connection
    Missing Earth
    Loose Neutral Connection
    Missing Neutral

    I have been thinking about making an alarm when there is an Earth/Neutral fault.
    Bearing in mind that this is to be a permanently connected device, could one measure a voltage between these two points, and if it raises above a certain value, then one could consider that it is a fault.
    The question is, at what minimum voltage between Neutral and Earth does one consider to be a fault, or would there be a voltage difference between the two if there was an issue with the Earth connection?
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    SANS 10142-1

    Reg 8.6.6 states that if the voltage between neutral and earth exceeds 25 Volts, then the Supplier must be notified.

    Should the voltage between neutral and earth exceed 50 Volts, then the supply to the installation must be disconnected.

    From the above, it would seem that any voltage above 25 Volts can be seen as a fault.

    Derek

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    Quote Originally Posted by Derlyn View Post
    SANS 10142-1

    Reg 8.6.6 states that if the voltage between neutral and earth exceeds 25 Volts, then the Supplier must be notified.

    Should the voltage between neutral and earth exceed 50 Volts, then the supply to the installation must be disconnected.

    From the above, it would seem that any voltage above 25 Volts can be seen as a fault.

    Derek
    Just imagine if we did as this rule advises...the poor customers would be sitting without power for months/years ...have you ever tried to contact Ethekwini electricity department to get them to fix a problem.

    Not even 2 fire engines full of firemen standing around waiting ... while a building burnt because nobody could get hold of their electrical faults department...to save the building i ended up having to hit a steel rod through the cable to causing the fuse to blow so that the fire department could put out the fire.

    high loop impedance results havent even received any attention yet...emails sent weeks months and years ago still no response ...they dont seem to bother with silly this like this.

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    Diamond Member Justloadit's Avatar
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    Quote Originally Posted by ians View Post
    Just imagine if we did as this rule advises...the poor customers would be sitting without power for months/years ...have you ever tried to contact Ethekwini electricity department to get them to fix a problem.

    Not even 2 fire engines full of firemen standing around waiting ... while a building burnt because nobody could get hold of their electrical faults department...to save the building i ended up having to hit a steel rod through the cable to causing the fuse to blow so that the fire department could put out the fire.

    high loop impedance results havent even received any attention yet...emails sent weeks months and years ago still no response ...they dont seem to bother with silly this like this.
    Whilst I accept your experience with the local municipality, my brief by my customer is to protect his very expensive air conditioning control units, which blow the electronics due to these factors, and are then forced to replace under warranty at a huge expense.

    Once the protection equipment is installed, and will not run due to the power 'challenges' under protection, passes the responsibility over to the customer. It then becomes the customers responsibility to sort the problem out now, and not the equipment supplier.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Quote Originally Posted by Justloadit View Post
    Whilst I accept your experience with the local municipality, my brief by my customer is to protect his very expensive air conditioning control units, which blow the electronics due to these factors, and are then forced to replace under warranty at a huge expense.

    Once the protection equipment is installed, and will not run due to the power 'challenges' under protection, passes the responsibility over to the customer. It then becomes the customers responsibility to sort the problem out now, and not the equipment supplier.
    I have a customer in Durban which has had to install a trip connect...under and over voltage protection...massive UPS ...with a ton of batteries...because they do storage and computer/network support for companies...the supply to the building is so bad that every time the trip connect detects the voltage has dropped below 170 v (it was set to 180 but went off too often) it switches off the supply...the reason we installed a trip connect was more to protect the supply when the neutral cable was stolen (which happens often) ...they have decided to move to a new location...just imagine having light switch off and on 30 times a due to low voltage...the municipality did up the taps on the transformer...it worked for a week or 2 then back to the same issue.

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    Hi. With that neutral,earth and spike connection in the "cable entry box" before the db there shouldn't be voltage between neutral and earth. Or am I mistaken?

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