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3 phase 100A power supply - voltage at each phase goes up to 250+ Volts should I be worried?

Former Community Member
Former Community Member
New 3 phase power supply installed and live from an ICP (independent connection provider) and meter installed, the service is all sealed up and live.


My NICEIC electrician has now installed an 18 way distribution box after the 4 pole isolator from meter tails and everything seems to be all ok, we also made sure to achieve compliance with 18th edition amendment 1 as I have an electric vehicle on the property that will be charged.


I also got a 4 pole Type 1 surge protection device to be installed (Hager JK101SPD) in-line with the mains incomer so that all the ciruits behind it will be protect.


The car is protected behind a Type A and Type B RCD which is 4 pole and 40A (as per the manufacturer's guidelines). The charger also has other safety features such as earth monitoring and neutral-earth fault detection.

However, the car shows at peak and middle of the night the voltages around constant at 250V and sometimes sits as high as 257V (does not seem to go beyond that).


Is this something I need to be worried about? Or should be I be okay?


Appreciate your insights please.


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    Agreed - the official range for mains is 230V-6%+10% - i.e. anything between 216.2V and 253V. But then you've got the accuracy of your meter to contend with (which are usually a lot worse than you would hope). If it really is high then the DNO should do something about it - but it might be a fight. I've been on a commercial site where several of the UPSs were complaining of high supply voltage every night (probably >254V) yet the DNO's logger allegedly couldn't see the problem.


    If it's high on one or two lines, but low on the others - there is a possibility that there's a bad connection on the N and that's skewing things. (effectively the Ls are right but N (and Earth if TN) have moved from where they should be). That could be an early warning of quite a serious problem (broken PEN).

     




    I also got a 4 pole Type 1 surge protection device to be installed (Hager JK101SPD) in-line with the mains incomer so that all the ciruits behind it will be protect.



    Unusual - do you have lightning conductors on the building (or close by)? Generally a Type 1 is only specified where lighting in involved and typically only protects the type 2 SPD behind. Normally a Type 2 is needed to protect downstream circuits (and possibly a type 3 downstream of that to protect particularly sensitive equipment). There are combined Type 1+Type 2 where you need both at the same location.


       - Andy.
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  • 0

    Agreed - the official range for mains is 230V-6%+10% - i.e. anything between 216.2V and 253V. But then you've got the accuracy of your meter to contend with (which are usually a lot worse than you would hope). If it really is high then the DNO should do something about it - but it might be a fight. I've been on a commercial site where several of the UPSs were complaining of high supply voltage every night (probably >254V) yet the DNO's logger allegedly couldn't see the problem.


    If it's high on one or two lines, but low on the others - there is a possibility that there's a bad connection on the N and that's skewing things. (effectively the Ls are right but N (and Earth if TN) have moved from where they should be). That could be an early warning of quite a serious problem (broken PEN).

     




    I also got a 4 pole Type 1 surge protection device to be installed (Hager JK101SPD) in-line with the mains incomer so that all the ciruits behind it will be protect.



    Unusual - do you have lightning conductors on the building (or close by)? Generally a Type 1 is only specified where lighting in involved and typically only protects the type 2 SPD behind. Normally a Type 2 is needed to protect downstream circuits (and possibly a type 3 downstream of that to protect particularly sensitive equipment). There are combined Type 1+Type 2 where you need both at the same location.


       - Andy.
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