Hello,

I have searched this question but came up trumps so hoping you may be able to provide some guidance.

I have been producing some fault level and arc flash studies over the previous months using SKM PTW v8.0.3.5.

When using the Utility i have been completing two scenarios, one with the utility fault contribution at max and one with the utility fault contribution at min, and analysing the results to see which is worse case.
is there a way i can get PTW to complete the calculations at both max and min in one calculation.

i know that PTW does a calculation using BFC at each bus at 100% and another %age determined by the formulae in IEEE (formerly 85%), however, i my question is purely relating to the utility fault contribution.

in 90% of the cases the max and min utility fault contribution make no/negligable difference as the transformer through fault is minimal and the majority of the fault current at the busses is from the upstream Tx SCC.

however, for example i have a site where the max utility fault contribution is 1153MVA and the minimum utility fault contribution is 300MVA (i.e. a large difference).
in the above scenario all busses come out the same, with the exception of 3 (out of around 500 busses) which change from Cat 3 to Cat 4 on the lower utility fault contribution.

just wanting to check that i am correct in completing the calculations at max and min utility fault levels and whether there is a way in which i can put max and min into a utility and complete the arc flash calculation with one click of the button.

on the above example i am also completing IEC60909 fault level study and would like to show both results on a single diagram, the issue is however, the arc flash is worse case on the 300MVA scenario, the Fault Level is obviously worse case on the 1153MVA scenario, therefore i cannot show the SLD with the utility at both 300MVA & 1153MVA for each calc.

sorry for the rambling post, hope all makes sense.

any help greatly appreciated.

If I understand your question correctly you should be able to use the scenario manager to do that. Make your base project the maximum available fault current and Scenario 1 the minimum available and then when you run the arc flash study check the worst case box under the scenario button.

Great idea. I’ll give that a bash on Monday.

that works perfect, the only issue i am finding is that the SLD only pulls the information from that scenario in.

i.e. bus 1 is worse case in scenario 1, bus 2 is worse case in scenario 2, but i cannot get the datablock to show the worse case from both scenarios, instead it only shows that scenario result.

therefore the SLDs and the Results Table do not match (unless i print 2off x SLDs, one for each scenario - however, that would result in 24 SLDs which i dont really want to do).

any ideas.

sorted, found another datablock that is arc flash worse case.

much appreciated for your help

Glad to hear it and thanks for the update.

Did you find a Datablock Format Attribute that has the worst case? I'd be interested to see how it reports it, and does it state which scenario. This would be good to find for example when the scenario is emergency system transfer switch position E versus N.

You can edit the arc flash worst case datablock and add the scenario name in the editor.