# NCEES Power Morning Sample Question 137



## robertplant22 (Feb 5, 2012)

Does somebody knwo what the subscripts 3, and 1 onf relays 50/51 and 50N/51N mean?

I can't seem to fin any literature that uses this notation. I use a GE Relay application guide; however the notation on this guide is different than the one used on the problem.

Thanks


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## Ivory (Feb 5, 2012)

robertplant22 said:


> Does somebody knwo what the subscripts 3, and 1 onf relays 50/51 and 50N/51N mean?
> 
> I can't seem to fin any literature that uses this notation. I use a GE Relay application guide; however the notation on this guide is different than the one used on the problem.
> 
> Thanks


I think 1 is "master element" and 3 is "checking or interlocking relay"


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## Flyer_PE (Feb 5, 2012)

The 3 means that there are actually three discrete relays (1/phase) represented by the one symbol on the diagram. The 1 indicates that there is only one relay for the neutral OC function.


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## Wildsoldier PE (Feb 5, 2012)

Attached is a very important table for relays. EPRM doesn't have all scenarios . The one below is more complete. I used this exact table in the actual exam. Print it and keep it with your notes. Very important!!

Enjoy

http://www.ee.uidaho.edu/ee/power/EE525/Lectures/L9/RelayDeviceNumbers.pdf


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## robertplant22 (Feb 12, 2012)

Thanks everyone for chiming in.


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## saberger_vt (Jan 31, 2013)

Here are a couple more links to documents with relay information:

Eaton - Click on the "Section 01 - Power Distribution Systems" pages 95-99:

http://www.eaton.com/Eaton/ProductsServices/Electrical/YourBusiness/ConsultantsandEngineers/ConsultingApplicationGuide/index.htm

Or

ANSI numbers - ABB


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