With the events related to the energy transition, a shift from a traditional towards a decentralised power generate-on can be observed. The growing use of volatile, renewable energy sources culminates in the need for storage as well as transportation capabilities in the grids of tomorrow. Transmission and distribution grids worldwide are based on alternating current (AC), a well-established technology. This concept works reliable and stable but comes along with some restrictions. The transmittable power is limited by factors like the need for reactive power, which affects the maximum transmission length. Furthermore, dielectric losses as well as the skin effect limit the efficiency of AC power transmission. Due to these restrictions, the use of Direct Current (DC) can be beneficial. The Medium Voltage Direct Current (MVDC) power transmission is a promising approach to enhance the transport capacity of transmission links, such as cables or overhead lines. As several publications point out, the possibility of converting existing Medium Voltage Alternating Current (MVAC) overhead lines (OHL) to DC operation, the aspect of using overhead lines in such systems has to be investigated. Therefore, locally used MVAC insulators (Austria, Indonesia) as well as conductors are tested in terms of flashover strength and audible noise behaviour under DC-voltages. Environmental parameters like moisture, temperature and surface pollution are to be considered.