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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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    Mike,


    Thanks for the explanation. My the confusion arises from the values and the graph.


    The steady state curve shows a 2700A 3- phase fault. if I use the reactance values shown the values are not consistent.


    Steady state 2700A -> For a LN fault x2.5 -> 2700 X 2.5 = 6750A

    Zero sequence reactance is 7% for A 600kVA unit. This gives around 11.9kA


    Am I missing something?


    Thanks,

    Mike
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  • 0
    Mike,


    Thanks for the explanation. My the confusion arises from the values and the graph.


    The steady state curve shows a 2700A 3- phase fault. if I use the reactance values shown the values are not consistent.


    Steady state 2700A -> For a LN fault x2.5 -> 2700 X 2.5 = 6750A

    Zero sequence reactance is 7% for A 600kVA unit. This gives around 11.9kA


    Am I missing something?


    Thanks,

    Mike
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