Out of Step Protection

[Viceng]

Hello,
I was hoping for some help in setting up an out of step protection element on an SEL 300G. The manual calls for
- Generator transient reactance
- Generator step-up transformer impedance
- Impedance of line beyond the generator step-up xfmr

My question is: what if you have more than one generator on the low/med voltage bus before the step up transformer (assuming it is a bus tie between them with little to no impedance). Would one simply add the other X'd vales to the calculation or would they not come into play?

Thanks for the help.

 

[redfurry]

If you've got multiple generators on the tranformer low-voltage side, then it would seem you would need to take the combined impedance of the generators

(i.e - calculate the equivalent impedance of the parallel paths, which will give you an effective impedance which is lower than for a single machine).

For extra fun you will probably need to consider cases where not all generators are running so the effective impedance may vary.

Ian Dromey -

http://www.dromeydesign.com

 

[Viceng]

Thanks,

This could be a problem - Perhaps I could update setting groups based upon which generator(s) is running.

Has anyone else out there commissioned such a OOS scheme with multiple units? I would appreciate any settings recommendations.