Generator thermal damage curve

[mrbj]

Hi,
An earlier thread (238-118313) shows a Generator withstand curve according to NEMA MG1-16.45
Is there an equivalent curve under IEC / BS / European standards, and if so could someone direct me to it or post it on this site.
Is there a minimum recommended time that standby low voltage (400V - 250kVA to 1000kVA ) generators can withstand the sustained short circuit current, which I believe is typically 300% before damage to the alternator will occurr.
Regards,
mrbj.

 

[AMBMI]

I don't think that the thermal limit of a generator is an issue.
Usually the problem is detecting the small fault currents if the fault is close to the generator and the generator excitation system is affected (it's the reason why we use threshold voltage controlled elements ..51V).
I think that typical settings could be
I> threshold 115 % In, delay 3 seconds
I>> threshold 300 % In, delay 0.5 seconds
In any case the overcurrent protection is a backup protection. For internal faults the differential device should trip faster.