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Hello, Recommended practices and calculations for cable shield grounding and induced voltages are readily available for single conductor cables. However, I'm finding a difficult time in finding a similar reference or standard for 3-Conductor or trefoil cable arrangement (e.g. Teck). Does anyone...

Hi mLp85 - should the vector group you're referring to be "Yyn0" and not "YNyn0"? Wouldn't the Z0 of a YNyn0 be exceptionally low, and the tank effect being a consideration only where one of the Y-windings is open circuited (e.g. Yyn0)? Just bringing to back to my initial inquiry, here's a...

Good point, although 4kHz in this case.

Hello, I have an interesting current waveform at an industrial facility that appears to be quite sporadic (potentially occurring only once or twice a week), which very clearly has high harmonic content. This oscillography is only captured as there are fairly sensitive alarm elements programmed...

Thanks prc - is that 0.8-0.9 per-unit Z1 the same for a Yynd (floating primary)?

Thanks for the reply. So the buried delta will facilitate current flow for a secondary SLG fault? The question I would then ask is how would you calculate the zero sequence impedance for the SLG fault? If the buried delta (obviously rated much lower than the primary and secondary) facilitates...

Hello, For a Y-Yg transformer (primary floating, secondary solidly grounded), a secondary ground fault will have no current flow as there is no path on the primary windings for the necessary congruent current to flow. However, will this still be the case for a transformer with a buried delta...

Hello, Two years ago, I had a part of the slab of my house hydraulically jacked based on a recommendation of my contractor who was constructing a new bathroom. The following year, we had a significant amount of rain, resulting in a raising of the slab by over 2". Aside from the obvious...

I wonder how that works within the boundaries of engineering codes of ethics. Generally an engineer should ensure fair (market value?) remuneration for the professional service offered. As an example, here is an excerpt from the APEGBC code of ethics: (5) uphold the principle of...

waross pretty much nailed the intuitive explanation. The definition of "rotor angle" is the electrical angle between the machine quadrature axis and the synchronous reference.

Study work in question would be for power system related analyses (harmonic studies, transient motor starting, loadflow, short circuit calculations, reliability assessments, etc.). The study work is not directly related to an installation, but produced mainly to give an industrial customer...

Thanks for the replies. I've gone through several state engineering acts and yes, the provisions are generally congruent. However, where I'm not getting a clear consensus on is where the industrial exemptions apply. I have rarely, if ever, seen study work (ex. FEED, risk assessments...

Hello, I'm wondering if anyone knows off the top of their head or can point to the specific engineering act clause stating what work *specifically* requires the seal of a professional engineer. The work I'm looking for clarification on is some technical study work not related to any type of...

prc, this formula is very useful, thanks for the insight. Would you happen to know where it is cited (ex. J&P Transformer Book, Electric Power Transformer Engineering, etc.)?

Alternatively - where LVPCBs are already used, transfer systems can be programmed within a PLC or microprocessor relays for controlling the breakers. Usually provides the best flexibility and highest rating.

prc, that is great info. I have read through the "list of standards relevant to transformers" document you compiled, and cannot find anything which would strictly quantify this. Would you happen to know if there are standards or recommended practices with respect to designing to those...

Hello, I have scoured my technical documents regarding transformers and have not been able to find an answer to the below question. I am wondering if anyone would have an answer or direction to the following: For distribution transformers (~20-50MVA base), how close to the knee point is design...

You bring up a good point, LionelHutz. After reading ANSI C37.010 and C37.13, I couldn't find a stipulation explicitly stating the calculation methodology as described herein MUST be utilized in acquiring the maximum available short circuit currents for the purposes of confirming acceptable...

Hi Jeff, thanks for the quick reply. For the SCCR of the SSR, I've simply applied table SB4.1 to achieve the 5kA rating. However, what I am looking for is if there is a standard required as per UL 508A for the available fault calculation? For example, my ANSI rated circuit breaker requires...

Hello, I am looking to provide a rating for an industrial control panel with solid state relays (using UL 508A Supplement SB). I've been unable to find a reference to which standard the "available short circuit current" must be calculated. When rating gear and breakers, it is obvious - ANSI...