# Power PE 61



## yaoyaodes (Aug 12, 2021)

Can anyone explain to me the question 61? not quite understand the solution. Another quick question. the exam book from NCEES only has 80 questions, but when I search in the Engineer Boards, I saw a lot more. is there another exam study book has more questions?


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## DLD PE (Aug 12, 2021)

Every NCEES version of the electrical power practice exam is 80 questions. The older ones were simply numbered differently. While the 2020 version for the CBT is numbered 1-80, the older 2011 and 2017 versions were numbered 101-140 for the morning section, and 501-540 for the afternoon section.


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## akyip (Aug 13, 2021)

The key word in this problem is "instantaneously". Instantaneous basically means no time delay, or zero time delay.


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## yaoyaodes (Aug 13, 2021)

akyip said:


> The key word in this problem is "instantaneously". Instantaneous basically means no time delay, or zero time delay.


Thanks. is there a table for relay setting option explain? I am just curious what are other settings for.


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## Zach Stone P.E. (Aug 16, 2021)

The instantaneous overcurrent trip function typically operates with a time setting (or cycle setting) of zero. In other words, the current is so great, that the relay should trip the OCPD immediately without a time delay.


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## adamcarlisle (Apr 11, 2022)

Zach Stone P.E. said:


> The instantaneous overcurrent trip function typically operates with a time setting (or cycle setting) of zero. In other words, the current is so great, that the relay should trip the OCPD immediately without a time delay.


Are there any examples or articles that discuss how you would solve for the number of cycles if the trip function wasn't instantaneous?


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## Zach Stone P.E. (Apr 11, 2022)

adamcarlisle said:


> Are there any examples or articles that discuss how you would solve for the number of cycles if the trip function wasn't instantaneous?



Sure.

If you are referring to time delay overcurrent protection (ANSI #51) as opposed to instantaneous overcurrent protection (ANSI #50), the TCC (time-current curve) for the relay or overcurrent protection device will tell you how much time typically in seconds (as opposed to cycles) that the device will take to begin operating to clear a fault.

Here is a video I published not too long ago on the subject with examples of the TCCs graphs:

​


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## adamcarlisle (Apr 12, 2022)

Zach Stone P.E. said:


> Sure.
> 
> If you are referring to time delay overcurrent protection (ANSI #51) as opposed to instantaneous overcurrent protection (ANSI #50), the TCC (time-current curve) for the relay or overcurrent protection device will tell you how much time typically in seconds (as opposed to cycles) that the device will take to begin operating to clear a fault.
> 
> ...



Thank you very much!


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