OK thanks, I see what you mean now. The way I see it, I was looking at just the *network*, not the network+load system. In this view, you calculate bus A to bus B distances using just the admittances of the transmission network. In other words, the electric circuit we're considering here has all RLC impedances to ground of constant-power injections set to infinity.
What you're suggesting is interesting and more accurate, but I'm not sure if it is useful in practice (I'd like to know more). Say for instance that in one of the possible paths from bus A to bus B you have a load at some intermediate bus. If you use this load's RLC value (taken from some particular powerflow solution, of course) in the calculation of the Klein distance, it means you're considering paths going through the *ground node*. Which brings up this interesting question: under normal operation of power networks, can't we safely approximate those RLC values to infinity, since they are much greater than the typical RLC values of transmission lines and transformers? I have a feeling that we can do so, at least in transmission, but I confess I haven't checked the numbers. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 5:49 PM, Jovan Ilic <jovan.i...@gmail.com> wrote: > > Jose, > > Let me clarify. If you run a power flow you can obtain all the currents > and transfer the > constant P/Q loads into constant RLC you can rebuild your admittance > matrix with > this new RLC values. From here, calculating the electrical distance using > Z matrix > is nothing new. However, as soon as the load changes you have to do it > all over again. > My point is, you cannot have a single electrical distance matrix for a > given system. > > Paul, I know Paul Hines and I have read a couple of his group's papers on > electrical > distance. If memory serves, their approach suffered from the same problem > of > ignoring the load. This was a 3-4 years (or more) ago and they might have > made a > breakthrough but I'd have to do some reading, > > Another interesting approach that I ran into was based on the Jacobian but > I do not > remember the details. I have the paper somewhere and if somebody is > really curious > how it was done I can look for it. In that approach calculating the > equivalent RLC > load is not needed but again, the Jacobian changes with the load. > > I hope I made clear what I meant by my previous e-mail. > > Jovan > > > On Tue, Feb 17, 2015 at 11:26 AM, Jose Luis Marin <mari...@gridquant.com> > wrote: > >> Jovan, >> >> I agree it's not fast and efficient, as it involves inverting the >> admittance matrix. However, I do not see why not Klein's impedance >> distance could be used in power networks. I mean, the fact that some (ok, >> most) injections are expressed as constant power does not invalidate the >> fact that it's an electric circuit governed by Kirchoff laws. >> >> Incidentally, we have sometimes used the path of greatest admittance >> between two given nodes as an heuristic measure of "closeness" (actually, >> the net impedance of such path). It all depends what you want to use these >> distances for. >> >> -- >> Jose L. Marin >> Gridquant España SL >> Grupo AIA >> >> >> On Tue, Feb 17, 2015 at 4:35 PM, Jovan Ilic <jovan.i...@gmail.com> wrote: >> >>> >>> Paul, >>> >>> I would not call calculating Zbus "fast and efficient". Also, using >>> resistance distance >>> might make sense in standard electric circuits but it does not make >>> sense in power >>> networks with constant powers. >>> >>> As far as I know there is not a very good, theoretically sound, way of >>> calculating electrical >>> distance in power systems. I would love to be corrected on this one. >>> >>> Jovan >>> >>> >>> >>> On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe <paul.cu...@ucd.ie> wrote: >>> >>>> Hi Hans, >>>> >>>> There is indeed a fast and efficient way to calculate this, though you >>>> don't encounter it often in the power systems literature. >>>> >>>> You can use the Klein resistance distance, as defined here: >>>> http://link.springer.com/article/10.1007/BF01164627 >>>> >>>> Once you have inverted your Ybus matrix to get the Zbus, you can >>>> calculate the Thevenin impedance between any two nodes, i and j, as >>>> follows: >>>> >>>> >>>> >>>> Of course, the reciprocal of the Zthev impedance value will give the >>>> effective admittance between any two nodes. >>>> >>>> Hope this helps, >>>> >>>> Paul >>>> >>>> >>>> On 17/02/2015 15:06, Barrios, Hans wrote: >>>> >>>> Hello everybody, >>>> >>>> >>>> >>>> I was wondering if somebody had already the following issue: >>>> >>>> I would like to create a “full version” of the Y-matrix, i.e. a matrix >>>> where (as long as there is only one synchronous grid) the admittance >>>> between each bus is given, even if the bus are not connected directly by >>>> one branch. >>>> >>>> If I am not missing anything, the Admittance between each bus should be >>>> a simple calculation of parallel an series admittances. >>>> >>>> But I was wondering, if anyone knows a fast and efficient way I can >>>> used to calculate this also for big grid structures. >>>> >>>> >>>> >>>> Thank you in advance for your contributions! >>>> >>>> >>>> >>>> Best regards >>>> >>>> Hans >>>> >>>> >>>> >>>> >>>> >>>> *Hans Barrios Büchel, M.Sc.* >>>> >>>> >>>> >>>> Institut für Hochspannungstechnik / Institute for High Voltage >>>> Technology >>>> >>>> - Nachhaltige Übertragungssysteme / Sustainable Transmission Systems >>>> - Wissenschaftlicher Mitarbeiter / Research Assistant >>>> >>>> >>>> >>>> RWTH Aachen University >>>> >>>> Schinkelstraße 2, Raum SG 115.1 >>>> >>>> 52056 Aachen >>>> >>>> Germany >>>> >>>> >>>> >>>> Tel. +49 241 80-94959 >>>> >>>> Fax. +49 241 80-92135 >>>> >>>> >>>> >>>> Mail. barr...@ifht.rwth-aachen.de >>>> >>>> Web. www.ifht.rwth-aachen.de >>>> >>>> >>>> >>>> >>>> -- >>>> Dr. Paul Cuffe, >>>> Senior Researcher, >>>> Electricity Research Centre, >>>> University College Dublin. >>>> >>>> Phone: +353-1-716 1743 >>>> >>>> >>> >> >
