Discussion Forum

Hi Akim,

I am trying to perform similar calculations on HV Cable and I'm using Joule heating because it seems to be a better match to reality as we need to model the electric fields in the Cable as well (your simulation intention is not known).
The heating effect is a consequence of current flow and hence the temperature distribution. However, care needs to be taken to understand that the temperature rise is basically due to the losses and related to the voltage drop across the cable.

Regards
Tanumay

Hi Tanumay,

Thank you! I have attached my model, but the problem is that the solution does not converge. I don't know why. Also I wanted to add Volume Force, Inlet and Outlet but Heat Transfer in Solids does have them. Any ideas how can I add them? Also, in Magnetic Fields which one should I use to push current, Single Turn Coil or External Current Density?

Akim

Hi Akim

The probable reason for the non-convergence of your solution is the '0' value that you have used for the electrical conductivity values for Air, XLPE, Impregnated paper & PVC. 0 is the ideal value. This creates problem during the matrix computations of COMSOL (creating a null vector)
In this case you have to have to make an educated guess for low electrical conductivity values and input a very very small (but not too small) number. E.g. for air it could be 1e-14 S/m

Volume Force, Inlet and Outlet are available in Laminar flow or in other flow models

Single Turn-Coil is used to model highly conductive domains, such as, metal (Copper in this case). This current is to be modelled as current density here. Hence, I feel this is the correct node to punch in the current, however I'm not sure (This is simply my idea)
Good luck!

regards
Tanumay

Also do verify the correctness of the several variables that you've used for its defined values for giving-in numeric data.

Thank you Tanumay for your response! I will try. If I add laminar flow wil all three physics be coupled together? If yes, can you give me an idea how to do it or it is done automatically?
Variables? You mean the values in Parameters such as copper resistivity, density etc.?

You may couple Laminar flow either manually by adding Multiphysics node or by selecting a pre-coupled Multiphysics interface e.g. Conjugate heat transfer and couple it with 'ec'
'Variables' mean.. of the format... <identifier>.<variable_name> that is being calculated in your computation

What is the electrical conductivity value that you have used for PVC (Cable outer sheath)?
What is the reference source that you use for defining new materials?

for pvc i used 10e-16 S/m,
XLPE : 10e-14 S/m
Impregnated paper: 10e-14 S/m
Some of them i found from wikipedia, some from other sources.
I define heat source as abs(mf.Qrh), but when i run the simulation it gives no temperature increase or slight increase (less than 1 K). Am I defining heat source wrongly?

I also defined heat source as Electromagnetic heating, the same results

Hi Tanumay,

As you suggested I put non-zero but small values for electrical conductivity of air, pvc, xlpe and impregnated paper. This time following error shows up:
'Failed to find consistent initial values.
Complex number encountered.'
Do you have any ideas how can resolve this problem?

Thanks,
Akim