This study presents a new design of a planar transformer for dielectric barrier discharge (DBD). The requirements for such designs are mainly a high voltage ratio, a high voltage value at the secondary side, a specific shape for industrial applications (planar shape in this case), a low volume and a high dv/dt value at the secondary side for capacitive loads. So as to propose an efficient design tool to power electronics designers, the authors propose a virtual prototyping methodology based on an optimisation algorithm and a finite element simulation software. Towards this case study, power electronics designers can use this methodology (bi-objective optimisation algorithm) to treat new designs and especially for very innovative power converters for DBD reactors. The first objective is to pre-size the planar transformer (geometrical variables). Virtual solutions are proposed on a Pareto front: the power designer can chose the best one according to specific contexts (cost, shape, volume, efficiency etc.). In a second step, the authors propose experimental results and highlight the voltage probes modelling that must be taken into account in the case of very fast transient waveforms especially for capacitive loads such as DBD reactors.