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...
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...
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...
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...
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...
Hello Everyone,
Typically, when running a protection and coordination study or Arc Flash study we use time current curves to determined fault clearing times.
In some older facilities there can be protective devices (Relays, Fuses, etc.) which perhaps have been in service for an extensive...
Hello,
I was looking at the sample PE exam question below.
When solving the question i decided to use the XFMR Secondary voltage and MVA as my base values.
Which then required the Gen imp to be converted to the XFMR MVA base.
When doing so the first time i followed the process below...
Hello Everyone,
I was reading the IEEE C95.6 which is the "IEEE Standard for Safety Levels with Respect to Human Exposure to
Electromagnetic Fields".
In the document they mention the max limit with respect to electromagnetic field exposures as shown below.
What I'm not clear on is we...
Hello,
I was looking at the sample PE exam question below.
When solving the question i decided to use the XFMR Secondary voltage and MVA as my base values.
Which then required the Gen imp to be converted to the XFMR MVA base.
When doing so the first time i followed the process below...
Hello Everyone!
I have a sample SC calculation I'm looking at but can't seem to match the 3x3 impedance matrix found in the sample.
I have formed the Y matrix following the guidelines from Annex B in IEC 60909.
Attached are the system impedance details (pgs 1 to 2 of attachment), the sample Z...
Hello Everyone!
I have a sample SC calculation I'm looking at but can't seem to match the 3x3 impedance matrix found in the sample.
I have formed the Y matrix following the guidelines from Annex B in IEC 60909.
Attached are the system impedance details (pgs 1 to 2 of attachment), the sample...
Hello Everyone,
I came across a very interesting document recently from Schneider electric regarding virtual mains. It seems it's used as an AF mitigation technique in some cases.
I read there are two implementations.
The first is for systems where the HV of an XFMR has protection but the LV...
Hello Everyone,
In power system softwares i have seen that the UPS SC contributions are modeled by multiplying the FLA rating times a fixed multiplying factor.
I have seen this done to estimate the UPS SC contribution for the AC and DC outputs of the UPS.
I was wondering if anyone can shed...
Does anyone know if there are any publications with Typical values for gap between conductors for DC systems?
For example documents like IEEE 1584 have typical data for gap between conductors for ACAF Analysis.
I ask this since there are DCAF methodologies out there that use the gap between...
Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?
From my understanding, the "Rated Interrupting" current is the current the breaker can safely interrupt based on the max kV rating. This is then used to compare against the interrupting currents...
Hello,
Is Anyone out there familiar with the NENS 09 Australian AF Calculation method?
This method was published in the "ENA NENS 09-2014 National Guideline PPE Arc" Guideline that's used in Australia. (See equations below)
They list the methodology and equations but I don't see a breakdown...
Hello Everyone,
As many of you are aware documents like NFPA 70E 2021 publish shock protection boundaries for energized equipment.
After doing some research I saw that there is more than one document out there with shock protection boundary recommendations.
Some example are listed below...
Hello Everyone,
In the IEC world for capacitors with a rated voltage less than 1kV are governed by IEC 60831 which gives the following requirement for the discharge of capacitor stored energy when disconnected from a power source:
"the residual voltage shall be 75V or less within 3min"
Can...
Hello Everyone,
In the past, I have heard many engineers place high importance on modeling a generator's decrement Curve.
My basic understanding is that this curve represents the fault current that the generator can produce in the case of a 3-phase fault at the generator terminals.
What I...
