Denis Imamovic

Investigations of conductive particles in gas insulated Systems under DC-conditions

Gas insulated systems, have proven to be reliable for many years. But despite of a high availability some defects, in particular free moving particles can be very critical. Contamination with particles can result from mechanical abrasion or due to vibrations as well as the enclosures damages during the assembly. A further aspect is that power transmission with DC is getting more important. Therefore Gas Insulated Systems operated with DC will be required in the future. But particle behavior under DC-condition is much more different than under AC-condition. The aim of our investigations is a realistically determination of particle movement in a small scale set up with gas filled test vessel. An appropriate electrode arrangement was designed in order to achieve a similar utilization factor of a real size arrangement. To get an optimized field distribution, simulations by a FEM-program were undertaken as well as different electrode forms were used in the experiments. Experiments were carried out with different sizes of particles at different gas pressures with SF6-gas. In order to get a correlation between particle movement and partial discharge activity, a camera was synchronized with the PD-measurement. Finally statistical evaluation of the lift-off field strength was made for both polarities.

Underground transmission lines for high power AC and DC transmission

The latest state of the art and ongoing research about high power gas-insulated underground transmission lines as well as the latest technical improvements are presented in this contribution. The basic technology is presented and the advances of the technology with respect to different installation options are discussed. A very high power transmission capability, a low capacitance, lower resistive losses compared to power cables and overhead lines, negligible magnetic fields, no ageing phenomena of the insulating system and a maintenance free design are the main benefits. In consequence, GIL technology for high power HVDC transmission is actually under development.

Applications of underground transmission lines for high power AC transmission

Applications of gas-insulated transmission line (GIL) has increased in applied length and required power. World-wide underground bulk power transmission is getting more and more imported due to restricted available space and higher concentration of electric load mainly in metropoles and large cities. The increase of required electric power at concentrated locations requires power transmission solutions which allow maximum use of the available space. GIL is one technical solution which offers both requirements: highest power transmission and smallest space requirement. An outlook is given about the improvements of the laying process by using the concept of a mobile factory. In this paper a short overview of recently executed project by Siemens AG is given to give information about typical technical layouts and data. The chosen project can be seen as future references in application of GIL.