After re-reading carefully what I wrote, I can confirm that I actually said what I meant (which is not always the case).
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Oct 31, 2013, at 5:33 PM, spyros gian <[email protected]> wrote: > Dr Zimmerman, did you mean 'active' or 'reactive' in the first sentence? and > in the second sentence did you mean active as you wrote? > > From: [email protected] > Subject: Re: Nodal same-sign flows > Date: Thu, 31 Oct 2013 10:32:38 -0400 > To: [email protected] > > It is possible for the active power injections into both ends of a branch to > be positive, meaning there are active power losses in the line even though > the active “flow” is nearly zero. Presumably this is due to the currents > involved in the reactive power injections. I do not think it is possible for > the active power injections into both ends of a line to be negative, unless > it has a negative resistance. And I can’t think of a physical meaning for > negative series resistance in a branch. > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > On Oct 30, 2013, at 5:34 PM, spyros gian <[email protected]> wrote: > > Dr Zimmerman, > I would like to share with you an interesting observation. > Suppose a line connecting bus 1 and bus 2. > The power comes out of bus1, and goes into bus 2. So, 10MW come out of bus1, > and 8MW go into bus2. > The 2 MW is losses. > This sounds logical. > > However, there are cases in multibus systems, where across a line K-L, the > flow coming out of busK is 10MW > and the flow coming into busL is - 8MW. So in this case busK sends 10MW and > busL sends 8MW. > Is there a meaning in this? > > Also, there are cases where both powers are negative. > > I haven't got the files to send them to you, but in my experience I have seen > such cases occur with MatPower, though > I do not remember the versions. > > So the question is generalized into : > Can there be cases where the power that comes out of one bus and goes into > another bus of the same line, are of the same sign? > Is there any physical meaning into this ? > > Thank you > Syros Gian
