INVESTIGATION OF THE POSSIBILITY TO CONVERT MEDIUM-VOLTAGE AC OVERHEAD LINES (OHL) TO DC CASE STUDY: INDONESIAN AND AUSTRIAN MVAC OVERHEAD LINE

• Main Author: Surawijaya, Sinanuri
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/47864
• Institution: Institut Teknologi Bandung

With the events related to the energy transition, a shift from a traditional towards a decentralized power generation 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. In terms of audible noise, overhead line conductors operated with DC voltage do not significantly affect the increase in audible noise and the value obtained is around 23-30 dB. It is the same as rustling leaves and will not have a significant impact on the surrounding environment. Meanwhile, in terms of flashover voltage, taking into account light pollution, the possibility of DC voltage that can be applied to Austrian overhead lines up to ± 60 kV DC and the transmitted power increases by 408%. Meanwhile, for Indonesian overhead lines up to ± 40 kV DC can be considered and the power transferred can increase by 272%. From a technical point of view, MVAC overhead lines can be converted with DC voltage without replacing existing equipment. Only the addition of converter equipment is needed to convert voltage from AC to DC and vice versa. However, for determining the DC voltage used, knowledge about the geographical location and the resulting pollution as well as further line-specific calculations regarding insulation coordination are required.