How do you determine X"d, X'd, Xo on a small generator when the info is not given on the namepl 1

[bdn2004]

We've a fairly small generator .... 1800 rpm, 480V, 825kW and trying to model this in the power software.

I'm looking this up on the attached Red Book table... Is there a mistake on this table? It shows the X"d is greater than the X'd, why would that be?

 

[cranky108]

Most of the time that information is not on the nameplate. Someone needs to test for that information

Or if the unit is small enough, you can estimate it, knowing you will have a larger possible error in your calculations.

The truth is every time we have our generators tested, the numbers will be a little different. It might be the testing methods, or the losining of the coils, or something else.

 

[FreddyNurk]

For a machine of that size the data is typically also available via OEM datasheets, assuming that the OEM still exists and the machine is not too old.

EDMS Australia

 

[waross]

I'm looking this up on the attached Red Book table... Is there a mistake on this table?

I am wondering the same.
Is this the formula to determine fault current from that data?
Fault current limited by X"d = 1/.33 x rated current.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mgtrp]

Which version of the standard did you get that from? It doesn't match the my copy of the red book, which is the 1993 version (and I believe the still-current version), which show Xd" and Xd' headings on the opposite columns.

 

[7anoter4]

From EEP Network Protection & Automation Guide ch.5 page 52 [see attachment] since I"d is more than I'd then X"d<X'd.Somebody change the titles [X"d instead of X'd]
By the way, it is not the actual Table A4-1 from IEEE 141/1993. The actual table is this:

 

[bdn2004]

The attachment in my question is out of the Red Book (IEEE Std 141-1993) page 174. My version per the second unnumbered page is "Second Printing May 1996"

 

[waross]

9 June 1998Insert to SH16477IEEE Std 141-1993Corrections toIEEE Recommended Practice for Electric Power Distribution for Industrial Plants
Correction SheetIssued 9 June 1998The following corrections should be madeage 161: In 4.7.1 item a), the value of Xs should be changed from Xs = 15/Rs = 0.00165 per unit toXs = 15 ·Rs = 0.00165 per unit.Page 174: In table 4A-1, the column headings were reversed. The first column heading should be changedfrom Xd′ to Xd′′, and the second column heading should be changed from Xd′′ to Xd′. The corrected table is shown on the following page.

Corrections toIEEE Recommended Practice

Is there a mistake on this table?

Yes. There is a mistake in the table.

Bill
--------------------
"Why not the best?"
Jimmy Carter