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From the practice problems that I've done, if any of a transformer's sides is greater than 1000 V, then you have to use the table for over 1000 V for both sides of the transformer (even if the other side is not over 1000 V). If none of the transformer sides are rated over 1000 V, then you can...

These are the practice exams I used. Ranking them in my opinion/experience from most difficult (1) to least difficult. 1. Cram for PE Power Exam Volumes 1-4 2. Electrical PE Review Practice Exam 3. Engineering Pro Guides PE Power Full and Final Exams 4. Shorebrook PE Power Exam 5. PPI PE...

Bump. If they're not too busy, I would like to hear some input from some renowned experts like @Zach Stone, P.E., @Cram For The PE, and @justin-hawaii on this: whether each protective device type (fuses, circuit breakers, and protective relays) count as switching, interrupting, and sensing...

Zach, you're right. Thanks for the catch!

Yes, you're right. That IB, 240 should technically be IA, 240 in my equation for total A phase current... But IB 240 = IA 240 with the way I drew it 

Hey guys, I was doing a few examples involving the 1-phase split phase circuit... this is the circuit type that is common in residential homes. Can someone confirm if the current directions I drew up for this 120/240 V circuit is correct? It seems that each current must flow in a specific...

No, what I'm trying to say is that you use either the actual radius of the conductor (for a single conductor per phase) or the equivalent radius of multiple bundled conductors per phase. For the case of bundled sub-conductors per phase: Let r = actual radius of each sub-conductor, and d =...

This was something I was taught by a review session from Zach Stone, specifically about the NCEES reference handbook. GMRc should really be rc for the transmission line capacitance formulas. In general: When calculating transmission line inductance, you use GMR. When calculating transmission...

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I understand what you're saying about circuit breakers not really meant to be switches. I just find it odd that circuit breakers have thermal elements and magnetic coils that can be used to sense overcurrent, yet breakers themselves are not considered to be sensing devices. Especially since...

Another thing that sucks about the Code Book that it doesn't even list a Table of Contents for each section that lists a briefing of the code numbers and titles.

Well, I want to make sure what I listed is correct lol. It came up that apparently circuit breakers are not sensing devices and that protective relays count as switching devices... I thought that circuit breakers would count as sensing devices, since they have the thermal element and magnetic...

As @jd5191 mentioned above, one of the very confusing things that the NCEES reference handbook was use GMRc for the transmission line capacitance formulas. You actually just use the actual conductor radius for the transmission line capacitance. For the case of Problem 536, it's only 1 conductor...

And just to be clear on this. We don't actually bring in a hard copy of the reference handbook... They provide an electronic PDF version of the handbook for us... Correct?

Hey guys, So I was in a practice session, and a topic came up about whether fuses, circuit breakers, and protective devices are switching, sensing, and interrupting devices. I want to confirm that my understanding of these OCPD devices are correct. Fuses are sensing and interrupting devices...

This solution is basically doing a per-unit circuit analysis, using the positive-sequence values for the 3-phase fault. It's solving for S Gen = V Gen * I SC. Below is a good way to visualize what the solution is actually doing (in per-unit).

The voltages are stated to be line-to-line voltages. The first step divides the voltages by sqrt(3) to change them into per-phase line-to-neutral voltages, for simple 1-phase equivalent circuit analysis. Then at the end, the multiplying by 3 occurs because: Q Line, 1-ph = I^2 * X Line Q Line...

I don't have an explanation for the NCEES formulas, but typically for such lighting problems I just use: Lumens = (E * A) / (CU * LLF * BF) E is just your given illumination in fc or lux A is room area, in ft^2 or m^2 CU is coefficient of utilization. LLF is light loss factor. If not...

Also, there are questions about solving for a transformer's actual impedance on one given side, given only the per unit impedance and the ratings of the transformer.

Questions involving change in per-unit impedance due to a new system base are very common. If you have the Power System Analysis textbook by Glover/Sarma/Overbye, their transformers chapter (Chapter 3, I think) has a few good examples on using the per-unit method for a simplified analysis of a...