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If I use 392.80 to determine the ampacity of the conductors in a cable tray, how do I rate the ampacity if the conductors leave the tray in a raceway for approximately 6' and terminate at a switchboard? Do I need to follow 310.15 for raceway? Is there a maximum distance I can run them in...

Has anyone actually done the calculations in c57.116? I am confused because I thought they were solving for generator PU voltage based on the system voltage and generator max vars. However, the equation appears to be calculation the system voltage and mixing actual units with PU. Additionally...

So why does a wye-delta work? The delta can't pass the zero sequence current, so why does it provide a grounding path?

Typically the zero sequence CT or (BYZ CT) has a low ratio (50:5)and is utilized on medium voltage motors because it cane be set at very low trip settings (10-20A). Neutral ct's typically have much higher ratios to allow for downstream coordination.

A zig-zag was my first design preference, but the customer is arguing to establish the ground by ordering a wye-wye unit transformer (2000kva). I modeled the wye (gnd) - wye (gnd) in SKM and did not get single line to ground current. I tried drawing out the zero sequence diagram to understand...

Is there a reason why grounding transformer are wye-delta? If I had some auxiliary loads that I wanted to power from the secondary, could I make it wye (gnd) - wye (gnd)?

I am not a certified lightning designer, but I have seen UL master labeled systems connected to the building steel only at the top of the structure and then a ground loop outside tied to the building steel at the base.

I wanted to minimize any possible issues but I am having a hard time determining the pitch of the existing machine. I guess my question really is, does using either a zig-zag or a wye-delta grounding transformer provide a path for circulating neutral currents with the upstream 12,470v generator...

I have an existing 3MW generator running on a 12,470v wye system that is HRG. The 12,470 also feeds a 12,470 -2400 wye-delta transformer (ungrounded secondary). I want to add a 2400V generator to this bus, but also I was going to add a zig-zag grounding transformer to limit the over voltages...

I found an installation where a single phase 2400 L-N transformer was connected up using concentric neutral cable and the concentric portion connected to the neutral of the transformer. However, the cable was then spliced at a subsequent manhole to a single phase cable with a tape shield with...

I typically have set relays at or just above the cable ampacity/ or below the cable damage curve. It just seems odd that you can go into meticulous detail in fine tuning the cable ampacity (ie Nehr MCgrath calculations, temperature correction factors, circulating current calculations) and in...

So an Engineer could design a underground duct bank system with the complicated Neher - McGrath calculation but then set the overcurrent protection at 3x and have to rely on the customer monitoring and not to overload it over its usefull lifespan? To me that seems like asking for trouble...

I am curious why NEC article 240-101 which states the long time delay overcurrent protection on cables >600v can be set at 6x the ampacity is at odds with the ampacity tables. What is the thought process between the two.