Typically, only one of (5.7) and (5.8) will be binding, but both are necessary since you don't know (a) which direction the flow is going and (b) at which end the magnitude of the flow is larger. However, I have definitely seen cases where the limits at both ends of the line are binding at the same time (when using apparent power flow limits).
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Aug 1, 2013, at 11:37 AM, Sashireka Appalasamy <[email protected]> wrote: > Dear Dr. Zimmerman, > > Thank you so much for your reply, but could I then clarify that for each case > of branch flow, (i.e. power flowing from f (sending node) to t(receiving > node)) either only (5.7) or (5.8) is taken in consideration right(i.e.only > (5.7) is relevant as (5.8) is for when t is the sending node and f is the > receiving node right? ). > > Thank you once more for your time, > Sincerely, > Sashi > > > > > On Thu, Aug 1, 2013 at 11:34 PM, Ray Zimmerman <[email protected]> wrote: > 1. Yes. It is taken from the RATE_A column of the branch matrix. > 2. Ff gives the flow (apparent power, real power, or current, depending on > the option selected) in p.u. at the from end of all branches as a function of > a set of voltages and angles (which may or may not correspond to a power flow > solution). At the solution, in the case where Ff = Pf, then Ff = > results.branch(:, PF)/results.baseMVA. I don't think your rewriting of (5.7) > and (5.8) is quite equivalent since both Ff and Ft must be bounded by -Fmax > and Fmax, and either can be positive or negative, so Fft has to be the max of > the absolute values. > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Aug 1, 2013, at 7:48 AM, Sashireka Appalasamy > <[email protected]> wrote: > >> Dear Dr. Zimmerman, >> >> Just to let you know that I have a number of queries on equation 5.7 and >> 5.8, page 29 off the MATPOWER manual as given below, >> >> 1. Is the Fmax value the same for both the equations? >> 2. What is the value for Ff(theta,Vm)? Is it the same as >> results.branch(X,PF) for a given executed power flow and >> Ft(theta,Vm)=results.branch(X,PT) OR could equation 5.7 and 5.8 be written >> in the form -Fmax< Fft<Fmax which also means that equation 5.7 and 5.8 are >> only considered one at a time and that Fft value be equivalent to the max of >> (PF,PT)? >> >> Thank you in advance for your valuable time >> >> Sincerely, >> Sashi > >
