How can I define an equipotential surface/volume in FEniCS?

I want to solve electrostatic problem for potential. Charge density and medium permittivity are known, so is the potential of a grounded surface. I know how I can implement that.

But I would like to add an ideal conductor (of unknown potential) to the system. How can I introduce an equipotential surface/volume? I guess setting permittivity to infinity is not a feasible option?

• It increases the condition number and that increases the error. But if you choose a permittivity that is, say, $10^6$ larger than elsewhere, you should still be fine. Jun 27 at 3:24