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A continually growing demand for reliable energy supply makes existing power systems more heavily loaded and evokes engineers and experts to look for feasible immediate solutions in power energy transmission. One of these solutions might be a bulk power transmission network at extra high voltages based on direct current.
Currently, high voltage direct current (HV DC) transmission has been only realized in point-to-point systems and back-to-back arrangements. Thus, the next logical step in this development would be an HV DC network. In principle, it might have certain advantages over a conventional high voltage AC system, as it could be less closely meshed covering larger areas and transmit higher electric power with lower losses.
However, no well-grounded investigations concerning possible layout and operation of an HV DC network are publicly available. Experience from the HV DC lines does not allow to make substantial conclusions regarding the requirements for an HV DC network.
Therefore, some basic questions on the operation of an HV DC network need to be answered mainly from systems simulations.
With the recent developments in electrical transmission system, HVDC transmission for long distances has become feasible. With this development, many insulators are being used in HVDC system. Different kinds of insulators are situated at different places (example: desert, near to sea, agriculture area, etc.) so they will get expose to different types of pollution. Pollution affects the behavior of insulation in terms of breakdown and withstand capability. The application experience of insulators under HVDC conditions is limited. There is a necessity to understand the flashover performance and to recognize key parameters in the design and dimensioning of insulators used under HVDC conditions. This dissertation presents the difference between the analysis of partial breakdowns at AC and DC.
The dissertation explains the behavior of a water drop on insulator shed surface energized with DC. It deals with the moving water drop and hanging drop at the edge of the shed.
There are many situations where insulator structure should be in parallel. For example, the structure of insulators in vertical disconnector equipment often is parallel. If insulators are arranged in parallel, then the behavior of the electric field is totally different. It is important to know the behavior of these insulators used in HVDC system. This report also explains the pollution and non-pollution behavior of parallel insulators energized with DC.
The results can be a source of information to optimize the design and dimensioning of HVDC insulators, especially in pollution conditions.