This thesis contains the preparing steps of a voltage indicator’s design, which is used in gas insulated equipment. In the first step, we gain knowledge about gas insulated equipment and find out why we need the voltage indicator in such equipment. In the second step, we study the international electrotechnical standard of the voltage indicator and collect necessary information for the beginning stage. In the third step, by searching in different patent’s databases we can find what kind of realization is existed so far. After knowing their advantages and disadvantages, we choose a proper arrangement. In the forth step, we study software, which are necessary to make the chosen realization and with gained knowledge we create a beginning 2D model. We do a simulation with the 2D model and see how much voltage is expected on the sensor. In the fifth step, by virtue of the 2D model, we make a 3D model, which is more similar to the real arrangement. So with results of this model’s simulation, we can know how the voltage on the sensor depends on its sizes. Finally, we evaluate the gotten results and discuss problems, which are still not solved.