NCEES PWR Afternoon Sample Question 511

[seysan]

I am having a hard time finding |Vab| from NCEES sample question 511. I understand (70L-20/1000)(5+j10) is VaA. Can you tell me what the term 12.5/sqrt(3)L-30 (from the solution) is in terms of voltage? Is the delta load converted to a Y load and this voltage term is VAn on the load? Please explain why |Vab| is not |VaA + VAB + VbB|?

Any help would be greatly appreciated!

Sey

 

[Flyer_PE]

You're on the right track. The configuration of the load does not matter for this problem. It's just a black box being supplied by the cable with the listed impedance. The way to simplify this problem is to convert it such that it can be solved on a phase voltage/current basis. This turns it into a simple single phase voltage drop problem.

Hope this helps.

Jim

 

[seysan]

Thanks for the help Jim! I think I understand the problem/solution better now.

 

[pete25]

Thanks for the help Jim! I think I understand the problem/solution better now.

Can this problem be solved using Line to Line values? IF so, I cannot seem to get it solved that way.