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Hahha. Going home in good mood with a feeling of passing it. IMHO Go lesser side. 

Thanks. IMHO it takes into account Setting calculations of the largest motor as per 432.52 Plus FLA of other motors. 

I think not more than phenomenon is also applicable to Motor feeder  SCGF protection- 430.62.A?

GMD (D12*D13*D14*D23*D24*D34)**1/6 is correct for 4 conductors.It is always a multiplication and then 1/n th root if n is the nos.

Thanks a lot. Lol. I was part of that discussion. I just wanted to double check if the group has become wiser after that. I myself updated my wisdom for that Motor OC thing during this time. 

@Stephen2awesome How do you explain  #CI-I-69. where he asks largest allowable current for O/C device to protect 300kcmil, (TW) 60 degree Celsius, Aluminium Conductors in steel conduit feeding a 277V load. From table I get Ampacity as 195A. Now which option is true  for answer 180A or 200A and...

Trying to define NEC NEC is a standardised Engineering document prepared by Engineers to be followed by non Engineers. When a non Engineer refers it, he simply follows it, when an Engineer refers it, he follows it with reasoning and sometimes questions it because one can not tame Engg into one...

I too thought on similar lines. Thanks for the explanation.

Makes sense. Now a new question for consideration. If a motor with 60A needs a feeder ckt of 1.25*60=72A  and a capacitor rated for 60A is connected somewhere near motor terminals ( A hypothetical case for understanding purpose only), will the motor feeder ckt conductors now required be 1.35*60...

Yes, you are true. There is a question in NCEES  sample Qs -#510. The answer is  according to your suggested way. Thanks a lot Omer for raising the issue and to all contributors in this thread. I really learned it today, at least to get correct answer in the Exam. But for this thread I was going...

It depends Omer. It will depend on the completion of circuit path for zero sequence currents.  In case of a star connected winding,the zero sequence  currents will flow only if star is grounded (Neutral) and there is a path to ground or 4th wire. If there is no path to ground or 4th wire in this...

More I read and discuss NEC, more confused I am. Perhaps this happens when you want to explain science in arts way , you have to use so many ifs and buts. Coming to the point, even though 430.32.A.1 says "not more than......." ; 430.32.C permits a higher capacity overload device if selection by...

You are more right sir.

Something is here. I do not know how useful is that.  http://machineryequipmentonline.com/electrical-power-generation/transformerstransformer-polarity-terminal-markings-and-connections/

 I was wrong. It is 0.5pu. @FParit does not ask about currents, It asks about +sequence Voltage. IMHO your currents are also wrong. The Positive and negative sequence currents are 1.6pu and -1.6pu respectively. The 1 pu I was mentioning earlier, was Vf ie. Fault Voltage - that is also positive...

Is it 1 pu? Base 34.5kV.

In this case the 13.8 KV left side bus supplying the power has no given Z, so it becomes infinite bus implying the bus with perfect constant Voltage or a source with Zero internal Impedance. Had the Z for bus been given, which sometimes come in form of Short Circuit capacity, that needs to be...

You are right Omer. In this case it is true because it is a load current and the Thevenin Impedance is small compared to load Impedance and can be neglected. You will realise the difference when say, I give  you a load impedance of say 0.5 Ohms. Try and do it.

While using actual impedances, make sure that they are transported at one end, either Gen end or Load end (at one Voltage to be more specific), through Transformers by that square formula else you get a wrong answer.

Rarely we find a good explanation on use of pu system. The author has shown patience to explain it in nice steps, making sure that no gap is left while delivering the information/knowledge. Very excellent explanation of how to use pu system. My compliments to Zach and his team at @Electrical PE...