In my opinion, in most cses computer solutions are much esier using nodal admittance methods once you select a node as a reference then it is very easy to set up an admittance matrix yii is the sum of admittances connected to node i from all nodes including the reference. yij=yji =-sum of admittances between i and j. There is no row or column related to the reference node. Invert this matrix to get a Z-Bus matrix which is a generalized Thevenin impedance The resultant zii terms are the driving point impedances (thevenin impedance between i and reference. for impedances between nodes i and j use zii+zjj -2zij which is the thevenin impedance between i and j Zbus can be built in steps avoiding inversion of a large matrix. This method is shown or should be shown in modern power system texts as it is very useful for fault analysis of large systems.
Don ----- Original Message ----- From: "Aai" <[email protected]> To: [email protected] Sent: Tuesday, January 8, 2013 9:23:43 AM Subject: Re: [Jprogramming] xkcd 356 In fact this method is like measuring resistance with an okmmeter between points A and B of the network. FWIW here is my interpretation/translation of the Maxima code: nbrs=: 1 3 5 7&{@, swz=:0,.~0,.0,~0,] resistornw=: 4 :0 'h w'=.x 'al bl'=. (+w&*)~/"1 y d =.(*=/~@i.@#) #&> ix=.,3 3 <@(<:#~0~:])@nbrs;. _3 swz 1+i.h,w r=. 1 al }zv=.0$~h*w A=. %. r (al)} d + _1:`[`]}&zv&>ix bl { A +/ .* 1 bl }zv ) Your example is calculated like: 2 2 resistornw 0 0,:1 1 1 Or as David pointed out: % +/ % +/"(1) 1 1 ,:1 1 1 On 08-01-13 17:24, Raul Miller wrote: > I'm a bit confused by the maxima solution. For example, A is both a > specific node and it's also a 10 by 10 matrix. Similar for B. I can > assume that the matrix values are something like potential > contribution from the named node. But... k looks like the 10 10 #. > of an index pair (with a bit of off-by-one since the maxima solution > is using 1 based indices) except it's used as an index into A and B. > And... so maybe A and B are really representing logically different > kinds of data in different parts of their structure? But what is the > logical structure then. > > ... anyways, the purpose of some of this code is not clear to me. > -- Met vriendelijke groet, @@i = Arie Groeneveld ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
