A 1,000 KVA, 12.47KV- 480Y/277-V transformer with 4% impedance feeds a 480-V bus. The fault duty of the 12.47-KV system is 40MVA. Assuming the transformer and the 12.47KV system have the same X/R ratio, the 3-phase short circuit current(Amperes) avaliable at the 480-V bus is mostlynearly: I am having difficulties visualizing this problem. Can you anyone tackle this problem on a step by step process?. -What so they mean by same "X/R ratio"? Thanks ..read more

I get confuse of the reply for this problem from thread http://engineerboards.com/index.php?showto...;hl=NCEES+Power IF the rating of the input of the transformer is 50KVA, should the output rating also be 50KVA ? Consider the transformer as a black box, what make the output power is greater than the input power ? Thanks ..read more

I don't think #136 is in the index. Anyhow, I don't agree with the answer so hopefully someone can help me out. Voltage drop = I|Z| where Z=Rcos(theta)+Xsine(theta) and |Z|=sqr[(Rcos(theta))^2 + (Xsine(theta))^2] unity power factor: Z = .05cos(0)+0.05sine(0) = 0.05 + j0 and |Z| = 0.05 zero power factor: Z= .05cos(90)+0.05sine(90) = 0 + j0.05 and |Z| = 0.05 0.707 power factor: .05cos(45)+0.05sine(45) = 0.0354 + j0.0354 and |Z| = 0.05 therefore, the voltage drop would be the... Read more ..read more

A synchronous generator is 3 phase wye connected and rated 1131 kva, 2.4 kv, 0.9 lagging. the output current from the generator at rated full load is most nearly: Why do you use the formula Sbase = Sq root 3 Vbase Ibase I just used the S=VI formula and got it wrong. Tad confused ..read more

I took the plunge and decided to try out the HP 35s. I was working my way thorough the user's guide and trying out some of the examples. I entered the Time Value of Money equation per the user's guide and I keep getting the "MEMORY FULL" message. I got this before when trying out another example and I had to delete saved equations and programs before the message went away. There is no way that I have come anywhere close to the 30k of user RAM that is stated in the specs. I simply entered a... Read more ..read more

A line ground to fault occurs by the primary side of a delta wye transformer T2 of impedance 6%, The question is concerning the location to clear the fault 1) Position A at the other end of the transmission line , 2) Position B at the same transformer 3) via both positions ..read more

Can anyone help me with this question? I am not sure if I understand the tap setting correctly. I am not quite sure what is restraining winding tap setting. I am assuming that because the two currents (4.8A and 8.3A) on the two sides of the relay are not equal, so there is another CT to make the 8.3A equal to 4.8A? if that's the case, can we step up the 4.8A to match 8.3A ..read more

It seems I put my question in the wrong section, so I'm reposting it here: Hello! Here's a question from the Pratice Exam I'd like some help on: The correct answer is C. I understand that only CS4 and A15-13 matter for the answer... I just don't understand how. Could someone please walk me through this problem? Explain it to me like I'm idiot? Thanks ..read more

Can anyone explain to me the 9.2t. I am so confused about the distance relay topic ..read more

Can someone explain to me where 3337 comes from ..read more