Yes I can understand your explanation now. I want to define the flow based on the average which means it will be sum of MVA_flow_from & MVA_flow_to divide by 2. Once again, Many thanks.
Idris Musa From: [email protected] [mailto:[email protected]] On Behalf Of Ray Zimmerman Sent: 26 May 2011 18:55 To: MATPOWER discussion forum Subject: Re: total MVA flow in a branch I think you may have missed my point ... since some of the "flow" is lost in the line itself, the apparent power entering the line at i and the power leaving the line at j will be different. So you have two numbers. Which one do you want to use to represent *the* "flow"? the flow at i? the flow at j? the min? the max? the average? How you choose to define "flow" in this case, I suppose, is a function of how you intend to use it. -- Ray Zimmerman Senior Research Associate 211 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 26, 2011, at 1:22 PM, Idris Musa wrote: Dear Dr Ray, Thank you very much. Yes I was referring to radial network. By 'the total MVA flow' I am referring to MVA flow between any 2 nodes(say, i & j). I am trying to compute what will be the MVA flow through the branch given the branches values of PF, QF and PT, QT injections from the power flow results. Idris -----Original Message----- From: [email protected]<mailto:[email protected]> [mailto:bounce-32610422- [email protected]] On Behalf Of Ray Zimmerman Sent: 26 May 2011 17:32 To: MATPOWER discussion forum Subject: Re: total MVA flow in a branch I think you have to define "the total MVA flow in a branch". In the standard branch model used in MATPOWER, there are losses in the branch, so the flow at one end and the flow at the other are not equal, so there isn't a single value of MVA flow that is *the* flow. The OPF flow limits are based on the max of the two. Or you might want to use the average, but certainly not the sum. I'm not sure what you mean by the "first branch" and the "source", unless you are referring to a radial system with a single generator. In that case, the P and Q flows at the end of the line connected to the source should match the generation at the source (assuming there are no shunt elements and loads at that bus). -- Ray Zimmerman Senior Research Associate 211 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 26, 2011, at 6:04 AM, Idris Musa wrote: Dear all, How do I compute the total MVA flow in a branch? if MVA_flow_from = sqrt(results.branch(:, PF).^2 + results.branch(:, QF).^2); and MVA_flow_to = sqrt(results.branch(:, PT).^2 + results.branch(:, QT).^2); Can I add the 2 results above directly to give me the total flow in a branch? If Yes then I expect that sum of the MVA flow in the first branch when I run power flow should reflect the total generation from the source. Else how do I go about it. I would glad if someone could put me through. Many thanks Idris
