Recent content by Wfg42438

Thank you for the insight is there any way you can point me to a good source to obtain the relevant impedance values for my particular case?

Thank you so much for the feedback and sharing your practical experience. I feel more comfortable with this particular case now, thank you!

Hello, I wanted to see if anyone has a good reference of how to determine the per unit impedance of 3 Winding XMFRs ? I have a very basic fictious system shown below and I'm trying to determine how to by hand calculate the LG and 3 Ph fault currents at Bus 23, 26, and Bus27 but I'm not clear...

Thank you for the detailed response. If you are willing to quickly look at Figure 3 of the article in the link from cummins there is a time after the transient region where the L-L and L-G currents are larger than 3 Ph for the generator in the sample Any comments on why after some time the LL...

Hello Everyone, I was reading this article on generator decrement curves created by cummins and its was quite interesting. On Figure 3 of the article, they show that in there example for a terminal fault at around 0.1 seconds both the line to line and L-G fault currents are larger than the 3Ph...

Thanks for the feedback I get where you are coming from thats its most common 3Ph currents are worst case. Do you mind elaborating on the 15% allowance for the equipment rating? Can you maybe break it down in terms of an example, lets say a CB has an SC current rating of 50kA how does the 15%...

Hello Everyone, In section 7.2 of the IEEE 399 book there is some discussion about 3Ph faults vs LG fault for protective device duty analysis. (see attached image) Typically its most common to focus on the 3Ph faults however for the special condition where LG faults results are larger than...

@System Protection The question that comes to mind is why use "3 * I Zero Seq Current" over the other available results (seq or phase currents for example)? Would one example of this results relevance be for a fault on the secondary of a XFMR with Y-solid grounding since the neutral current...

Hello Everyone, I am in the middle of trying to further understand symmetrical components. The SEL paper below has been a great resource. https://cms-cdn.selinc.com/assets/Literature/Publications/White%20Papers/LWP0010-02_TutorialSymmetrical-Pt2_AH_20201019.pdf?v=20201020-155433 I notice...

@7anoter4 Thank you so much this is exactly what I needed!

Would anyone in this forum have access to the C22.1-21 Canadian electrical code published in 2021? I’d like to confirm is if any changes have been made to the capacitor discharge requirements shown in red in the image below from the 2018 version.

I have seen some discussions about considering the zero-seq magnetizing current for secondary side fault of a XFMR with Wye grounding on the primary and y solid grounding on the secondary. I am curious if anyone knows any good references that goes into an example calculation for the LG fault...

@davidbeach Thanks for sharing such interesting information on what youve seen out in the field. Based on what you have shared it seems there is some wiggle room in there for error. However, there is no set guideline to say what to do in all cases as expected.

@thermionic1 Thank you for the feedback from what you have experienced. From what you have seen where you expect a +/- 3% tolerance it seems considering this in the FCT wouldn't be the worst idea. However, I do realize an extra 3% tolerance is not going to make a significant impact just...

@dpc I agree with your statement 100%. In the relay case the FCT= Breaker Opening Time + Relay Tripping time. My question is based on the equipment's age could one introduce a "%Tolerance" on the relay trip time? For example something along the lines of : FCT= Breaker Opening Time + Relay...