Optical and electrical acquisition of discharge phenomena on air gaps

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In simulation software like ATP/EMTP, there are only inaccurate models to simulate very fast transients in power system due to lightning strikes. The lack of knowledge about physical processes in case of flashover on insulator caused by lightning strike on overhead lines is the main imperfection of such software. Therefore, some standard parameters like a safety factor are considered for insulation coordination calculations. Hence, the main goal of this research project is to overcome the issue by measuring the existing processes in case of lightning flashover on insulator because of a lightning strike in power systems. Moreover, the measurement results should be physically interpreted. To provide a physical comprehension about lightning flashover, a developed measurement system with a rod-rod electrode will be used. The most frequent flashover on insulators can be reproduced by a rod-rod electrode arrangement and thereafter, voltage at the impulse generator and the current at both electrodes can be synchronously measured.The main challenge here is not only the flashover current measurement but also the pre-discharge current measurement. After performing a variety of measurements, the parameters of flashover such as charge quantity, propagation of charge carriers in air gap and the polarity of the applied voltage will be calculated. Furthermore, it will be compared to/with the rod-plan electrode arrangement, which has been already investigated.With the aid of empirical and statistical investigation, the individual phases of flashover for rod-rod electrode arrangement under standard lightning impulse voltage should be identified and described. These results are the base for a detailed modelling of the physical processes during a lightning flashover.Further goal of this research is to provide a basic knowledge about processes under non-standard, oscillatory lightning impulse voltage in order to investigate the lightning flashover that occurs on insulation in reality. To this propose, a further measurement setup should be constructed, which should be supported by the fund of this research proposal. Consequently, measurements should be carried out by the developed system in order to identify the differences of discharge processes under standard and non-standard, oscillating lightning impulse voltage.