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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.


  • 0
    It is normal for voltages to move around a bit, although the 257V you suggest is a bit higher (253V) than one would expect. To measure this properly one needs a high accuracy true RMS meter (0.1% or better) which you may not have. It is not a cause for concern anyway, and is very unlikely to damage your car.
  • 0
    HI FaeLLe


    I assume the ICP has connected you to the national grid - a public supply - and not a private supply? I assume you don't have your own transformer? 


    In which case - other than maybe the 4 pole isolator - and how that makes/breaks the neutral; I'd let the national grid worry about the amount of volts they put out there. The kit can almost certainly take 257V. 


    All should be OK I think.


    Kind Regards


    Tatty
  • 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.
  • 0
    If these voltages are reported by the car software, they may not be that accurate  (5 to 10% off does not affect the cars internal 'is it OK to charge' decision)- if you are concerned, a then a comparison with readings from a proper meter is needed.

    Officially the supply may be 230V +10%-6% , so 253 would be the upper bound for 'normal' operations.


    In use quite a bit of voltage variation is not normally a  problem unless there are other indications the voltage really is a bit high, the classic used to be failing light bulbs, but less so nowadays with electronically ballasted LEDs and so on.

    It may be set up wrongly if a new transformer has gone in to support your supply, and the wrong tap connections  have been set, or if for some reason lots of generation has been added to your substation (I'd think solar panels as a source of voltage rise, but obviously not if the volts only go up at night ?.)

    Before panicking, I suggest a cross check with a real meter, or seeing what the car  reports when charging elsewhere.

  • 0
    As I pointed out, you must use accurate metering of a particular type, which must be a very accurate true RMS meter. Normal average reading meters are no good at all if the waveform is even slightly distorted. Data loggers are of this type. Normal multimeters are usually average reading, RMS calibrated, so not much use. The car accuracy is probably very dubious! Its charger will be very well protected against most mains incidents, spikes and excess voltages, including automatic disconnection if it is not happy.
  • 0
    Is it 257 volts whilst the car is charging or when the charger is offline?


     Andy Betteridge
  • Former Community Member
    0 Former Community Member

    tattyinengland:

    HI FaeLLe


    I assume the ICP has connected you to the national grid - a public supply - and not a private supply? I assume you don't have your own transformer? 


    In which case - other than maybe the 4 pole isolator - and how that makes/breaks the neutral; I'd let the national grid worry about the amount of volts they put out there. The kit can almost certainly take 257V. 


    All should be OK I think.


    Kind Regards


    Tatty




    Thank you for the reassurance Tatty! I was told that sometimes the live cable joining that happens at the street could cause issues which might cause voltage fluctuations.

    When my electrician who put up the distribution box measured the voltage it did show 240 to 245V at each live cable , was just wondering if things might have varied since then especially at off peak times (after midnight) when unused voltage was all flowing across to me.


    Also the fact that the electricity substation with the LV board is right next to my property did give me a bit of a scare.

  • Former Community Member
    0 Former Community Member

    AJJewsbury:



    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.

    [1] If I wanted to get the DNO to take a look what information might I want to give them? Would they just disregard it by saying your meter is just faulty?


    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).

    [2] Broken PEN has been something I was paranoid about so I got an ABB device that monitors earth and neutral breaks, I think it is called RC223.

    Basically have it to protect the outdoor EV charging point to comply with 18th edition amendment 1; did not want to have someone wandering around touch the car when it is wet and get electrocuted.




    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.

    [3] No lightning conductors nearby but I just wanted some assurance or protection from surges as the electricity substation is next door and the LV board is maybe 12 feet from my distribution box! I know it is the DNO's responsibility to not send surges down but hey I have several thousands worth of IT kit behind their network and if it goes out I am the one who gets impacted.....


    Hager technical support teams told me the Type 1 SPD would protect all the cicruits in the DB and give it Type 2 and Type 3 protection as well :/

    I just looked at the documentation and it looks like it is a Type 1 and Type SPD....


    What is the best practice around SPD's should I consider any other type of protection for mine? I know the regs say it is based on risk assessment but what does that really involve?

    942523717075d8ac6b1199a56ac72ef6-huge-spd.png



       - Andy.

     




    Really appreciate all the  answers from everyone and I have got a lot more of insight than I expected so thanks a lot!

  • Former Community Member
    0 Former Community Member

    Sparkingchip:

    Is it 257 volts whilst the car is charging or when the charger is offline?


     Andy Betteridge




    Hi Andy, the voltage shown is what the car states when it is charging.

     

  • 0

    [2] Broken PEN has been something I was paranoid about so I got an ABB device that monitors earth and neutral breaks, I think it is called RC223.

    Basically have it to protect the outdoor EV charging point to comply with 18th edition amendment 1; did not want to have someone wandering around touch the car when it is wet and get electrocuted.



    Broken PENs are nasty things - not only is there the shock hazard from things that should be earthed, but there's the general issue of anything up to 400+ volts appearing between L & N - which tends to do permanent damage to a lot of equipment. SPD don't help much in that event either - they can only really deal with very short pulses of over voltages - not something that might last for hours or days.

     

    I know the regs say it is based on risk assessment but what does that really involve?





    Just plugging numbers into a formula and see if you get an answer above or below 1000. The numbers come from whether your situation is rural/suburban or urban, lightning flash density your location (the regs supply a map for the UK), and the features of the last 1km of the network that supplies you (whether underground or overhead and how much of that 1km is HV or LV). I can dig out the details if you're interested.


       - Andy.

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