Power System Stability

[chadwiseman]

I am looking for information on power system stability. In particular, we use synchronous condensers and many synchronous motors, and I'm wondering how this affects the stability of our power system (increases it or decreases it). Any informatin would be appreciated.

Thanks.

 

[alehman]

Can you be more specific about your question?
Power stability or voltage stability?
Incrase or decrease with relative to what?

 

[chadwiseman]

I am referring to power stability (i.e. how much power we can push through the transmission lines). Also, does the use of synchrous condesnsers increase the capability of the system relative to the same system without them (i.e. can we operate the power system at a greater power angle and still maintain dynamic stability).

 

[Alex68]

The stability of a system is its capability to reach a stable state after a disturbance.

Starting from this basic definition, what do you mean with power stability?

The presence of components able to regulate reactive power will allow synchronous generators to works with little internal angles (delta). Thus the gens are far from the static stability limit (delta = 90 degrees) and the stability of your system is increased.

 

[alehman]

Stability frequently refers to ability to maintain synchronism during transients as mentioned, but it can also refer to steady-state stability. For a simple 2-machine system:

Pmax = |Vg| |Vm| / |X|

This is a difficult question to answer. I think "it depends" is about as good as I can do. Stability calculations have traditionally been applied to large synchronous machines and long transmission lines. Stability is commonly discussed in terms of how one machine interacts with another or an infinite bus. It might be possible to consider an industrial plant for example, with a mix of induction and synchronous machines as one large induction machine and one large synchronous machine on a common bus with a remote generator (utility soruce).

I do not know how to evaulate stability of induction loads or how the overall stability may be impacted by concentration of synchonous vs. induction machines. There have been some recent articles on stability of induction machines as relates to wind turbine installations that may be helpful.

http://www.nrel.gov/docs/fy04osti/36199.pdf

http://www.actapress.com/PaperInfo.aspx?PaperID=15460

http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/transie4.html