the design of electrodes' and insulators' shapes with respect to electric field stresses in high voltage devices is formulated as a nonlinear optimization problem under constraints. we apply a sensitivity equation method in order to achieve gradient information for the optimal design problem. this enables us to use the sqp-algorithm for the optimization task while a fem software package accomplishes the electric field computation. results are presented for gas-insulated transmission lines and circuit-breakers in highly integrated switch-gears.