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Reference: ISH2015_102

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Experimental study on the influence of climatic conditions on the formation of ion currents at transmission line conductors under DC stress



Due to the arising demand for an increased transmission capacity and flexibility of the German transmission grid, the system operators have agreed on the integration of high voltage DC transmission (HVDC) into the existing German transmission system. Considering this development of the transmission grids, additional knowledge with regard to physical phenomena, e.g. corona discharges occurring at the surface of the conductors, becomes more and more important. For this purpose, an experimental setup based on a cylindrical corona cage, is developed in this research work for investigating the dependencies of ion currents in DC electric fields on climatic conditions implying temperature values in the range of ? = -15…40 °C and relative humidity values of ? = 20…90%. First experimental results show, that the measurements of the ion current activity of transmission line conductors yield a huge scatter of the occurring current amplitudes. Thus, a statistically verified analysis of the ion current activity requires multiple measurements with durations of several hours for one set of climatic and electrical conditions. Therefore, a methodology is developed which allows the identification of critical climatic conditions by measuring ion currents with low experimental scatter. On that score, the transmission line conductor is replaced by a smooth aluminium wire. The results obtained with the aluminium wire indicate a dependency of the corona onset field strength and the related DC component of the ion current on the air temperature, as well as an influence of air humidity on the ion current formation, once corona onset being exceeded. In addition, the experimental results for the corona onset field strength are compared to a commonly used calculation approach, yielding a good agreement.

File Size: 3 MB

Year: 2015

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