The use of vacuum circuit breaker technology in the high voltage level leads to new challenges for developers of vacuum interrupters. The larger dimensions of the vacuum bottle needs a field control system, which will be realised by multiple vapour shields.
In this study, specimens with various metal vapour shield models are examined.
To determine a dielectric strength, the test specimens have to be conditioned first. When conditioning with standard lightning impulse withstand voltage, it is not possible to specify certain withstand voltage. By changing the shape of the voltage pulse, the achieving of a certain withstand voltage is possible. The pulse shape is dependent on the values of the elements used in the pulse generating circuit. This paper deals with the impact of individual parameters on the conditioning behaviour and thus the factors for an optimal conditioning process.
Despite the better results through an optimized conditioning circuit, the scattering is relatively high. For this reason, not only the circuit parameters were investigated, the impact of manufacturing tolerances of industrially manufactured vacuum interrupters were investigated, too. It was checked how large the eccentricity of the metal vapour shields and ceramic are, and whether there is a connection between the point with the least distance between ceramic and metal vapour shield and the increased occurrence of arcing. Furthermore, it was also examined, whether there is a correlation between the locations where flashovers occur often and the surface roughness located there. Using a FEM simulation, the experimental data was further analysed. Places with high field stress were identified compared with places, were arcs actually originate.
From the results two findings can be drawn: Firstly, that the conditioning process de-pends mainly on the amount of charge, and secondly, that the triple point ceramic-electrode-vacuum affect the dielectric strength of a vacuum insulated electrode ar-rangement highly. | English |