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Diesel Generator Fault Levels

MG
Hello all,


I am looking to specify a temporary mobile diesel generator and as such looking into the disconnection times and the maximum fault current provided by the genset.

I have contacted a provider and got the specification of the alternator in their genset, images below of the fault current graph and the alternator per unit values.


I am looking into understanding what values to use. Am I correct in getting the sustained fault level and for an earth fault to apply the multiplication factor of 2.5 for sustained? I will make sure my disconnection times are less than the sustained maximum duration in order to not trip the generator breaker and loose all of the supply.


Alternator is 50Hz 415V

fc5681c638e7bada3947e466b96400fd-huge-newage-hci534e_1.jpg

3106a5e7994134e881a5487cbbe73194-huge-newage-hci534e.jpg


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  • Former Community Member
    0 Former Community Member

    perspicacious:

    If I've read the graph correctly, the set will provide just 2000 A at 0.1 sec. Will the preceding higher current be enough to operate the primary protective device and/or how far downstream? 


    Dare I mention RCDs?!


    Regards


    Bad BOD and Bed BOD till tomorrow



    Which would tend to agree with a rule of thumb that suggests (for a turbo diesel) that you'll get at best about 2.5 x FLC at 100milliseconds - which won't open most protective devices at Tier 1 or Tier 2 unless they are equipped with earth fault shunt trips (or are time stopped 100ms units with much lower pick ups (say 5 or 10 A)


    I suspect the problem here is Amtech can't model the fault current curves anything like as well as the manufacturers data  - it probably needs ERACS or similar to get some certainty


    Regards


    OMS
     

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  • Former Community Member
    0 Former Community Member

    perspicacious:

    If I've read the graph correctly, the set will provide just 2000 A at 0.1 sec. Will the preceding higher current be enough to operate the primary protective device and/or how far downstream? 


    Dare I mention RCDs?!


    Regards


    Bad BOD and Bed BOD till tomorrow



    Which would tend to agree with a rule of thumb that suggests (for a turbo diesel) that you'll get at best about 2.5 x FLC at 100milliseconds - which won't open most protective devices at Tier 1 or Tier 2 unless they are equipped with earth fault shunt trips (or are time stopped 100ms units with much lower pick ups (say 5 or 10 A)


    I suspect the problem here is Amtech can't model the fault current curves anything like as well as the manufacturers data  - it probably needs ERACS or similar to get some certainty


    Regards


    OMS
     

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