Droplets on insulators in outdoor high-voltage equipment move and leave water films on the insulating material. These films further the development of undesirable electric currents or even flash-overs. The paper deals with the behaviour of a single droplet laying on a solid support in a strong electric field. Inside the solid support two electrodes generate the electric field. Although the experiment is designed so that the electric field is nearly homogeneous in the absence of a droplet, the remaining inhomogeneity motivates the discussion of its influence on the droplet. Therefore, water droplets at general positions on the experimental set-up are considered. The deformation of the droplet is calculated together with the total force acting on whole the droplet. The total horizontal force initiates the droplet to move. An analytical proof of the existence of a non-vanishing total force acting on an extended uncharged body in a general electric field is given.
