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Join Date: Aug 2017
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Question About Power System Protection

08/28/2017 12:03 AM

Hi everyone, I'm new here (and also new to electrical engineering). I was working on some multiple choice sample questions about power system protection and was wondering if someone could give me some input. Distribution feeder is overloaded and the circuit breaker trips, which protection element sends the signal to the breaker to trip?

1. Distribution feeder is overloaded and the circuit breaker trips, which protection element sends the signal to the breaker to trip?

i) Instantaneous over-current

ii) under-voltage

iii) differential

iv) timed over current

2. If a phase to ground fault occurs on a distribution line, which protection element should operate first?

i) instantaneous over-current

ii) under-voltage

iii) differential

iv) timed over current

3. In a power system, switches are used to:

i) interrupt fault current

ii) control flow and isolate equipment

iv) Re-direct power surges

4. Thermal limits on equipment are mostly impacted by

i) system operational requirements

ii) system voltage levels

iii) customer load requirements

iv) temperatures

I'd appreciate it if someone can let me know if I'm on the write track with this?

Thanks!

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Guru

Join Date: Mar 2007
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#1

Re: Question about power system protection

08/28/2017 12:16 AM
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Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

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#2

Re: Question About Power System Protection

08/28/2017 12:24 PM

Go to the provided links, and then do your own homework, but careful, you might actually learn something.

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Guru

Join Date: May 2010
Location: Liverpool, NY
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#3

Re: Question About Power System Protection

08/29/2017 12:51 PM

And just to get you looking in more depth at the questions that were listed, only one of the 4 answers is correct (I won't tell you which). The answers chosen may seem to be appropriate ("common sense"?), but the application of protection systems is much more complex that that.

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Power-User

Join Date: Jun 2010
Location: Kolkata, West Bengal, India
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#4

Re: Question About Power System Protection

09/04/2017 7:35 AM

Before doing this home work please study thoroughly text book on Electrical Protection Engineering. After study , you will be able find correct answer of the above questions.

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Manindra
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Power-User

Join Date: Jun 2010
Location: Kolkata, West Bengal, India
Posts: 166
Good Answers: 1
#5

Re: Question About Power System Protection

09/04/2017 7:41 AM

Before doing this home work please study thoroughly text book on Electrical Protection Engineering. After proper study you will be able to find yourself correct answer of the above questions.

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Manindra
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Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

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#6
In reply to #5

Re: Question About Power System Protection

09/05/2017 1:37 PM

Yes, sometimes good advice bears repeating (themselves).

I do however often wonder why singular advice gets repeated twice. LOL

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