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problem in calculating capacitance of power transmission line

Posted Mar 13, 2011, 4:50 a.m. EDT Modeling Tools & Definitions, Parameters, Variables, & Functions 4 Replies

Puneet Malhotra
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Hi,
i am 3rd year electrical student using comsol 3.2. i am interested in calculating the capacitance of power transmission line. for that i modeled two parallel cylinders having radius 0.1m and length of 4m and put1volt and 0volt respectively and enclosed the whole arrangement in a cube of 10m length. on all six faces of cube i put boundary condition of zero charge/ symmetry . by using sub domain integration of energy density over the domain i found the energy in the surrounding region of two cylinders and by using the formula energy=(C*V^2)/2. but i am not getting the correct value of capacitance. please help to find out the error in my simulation .is their any edge effect. and how to avoid edge effect.

best regards
4 Replies Last Post Jun 15, 2011, 10:48 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 13, 2011, 6:12 a.m. EDT
Hi

v3.2 is very old (never had that one even, but I have some issues in understanding your model, is it only4m of cable length or is it a loong cable and you want to calculate the capacitance "per meter" length.

If you want the latter, I would rather use 2D , enbox with a circle rather than a square to avoid distorting too much the field lines by the box corners and try it out that way.

In the 3D case you have the end effects, and depending on your mesh and "sharp" corners you might end up wth singularities hence chances fornumerical errors. Validate carefully your model agains mesh density you might see an effect there too

--
Good luck
Ivar
Hi v3.2 is very old (never had that one even, but I have some issues in understanding your model, is it only4m of cable length or is it a loong cable and you want to calculate the capacitance "per meter" length. If you want the latter, I would rather use 2D , enbox with a circle rather than a square to avoid distorting too much the field lines by the box corners and try it out that way. In the 3D case you have the end effects, and depending on your mesh and "sharp" corners you might end up wth singularities hence chances fornumerical errors. Validate carefully your model agains mesh density you might see an effect there too -- Good luck Ivar
Puneet Malhotra
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Posted: 1 decade ago Mar 13, 2011, 2:40 p.m. EDT
Hi,
thanks a lot for your information!

i want to determine the capacitance of a finite segment(=4m) of long power transmission line. I construct a 3D model of two parallel axis cylinders. i am getting problem in putting the periodic boundary condition to avoid the the edge effect. please tell me how to periodic boundary condition so that i can avoid edge effect.

best regards
Hi, thanks a lot for your information! i want to determine the capacitance of a finite segment(=4m) of long power transmission line. I construct a 3D model of two parallel axis cylinders. i am getting problem in putting the periodic boundary condition to avoid the the edge effect. please tell me how to periodic boundary condition so that i can avoid edge effect. best regards
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 13, 2011, 3:13 p.m. EDT
Hi

In the never versions you set up an identity pair with a periodic relation, but I do not know what is, or not, implemented in v3.2.

Can't you do a 2D analysis ? just on a cut profile, or do you really have a periodic structure along the 4 meters ?

--
Good luck
Ivar
Hi In the never versions you set up an identity pair with a periodic relation, but I do not know what is, or not, implemented in v3.2. Can't you do a 2D analysis ? just on a cut profile, or do you really have a periodic structure along the 4 meters ? -- Good luck Ivar
Staika Simo
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Posted: 1 decade ago Jun 15, 2011, 10:48 a.m. EDT
I'm new to this topic Comsol with Matlab and I want to calculate the capacity between 4 different electrodes in matlab. how to deal with it.

best regards
I'm new to this topic Comsol with Matlab and I want to calculate the capacity between 4 different electrodes in matlab. how to deal with it. best regards

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