Simulation, Generation And Measurement Of Oscillated Lightning Impulse Voltage

This paper reports about the experiments to simulate and generate oscillating voltage impulses as well as to measure such voltage impulses. In the first part, the tower of overhead lines will be modelled in an EMTP program. The voltage across the insulator string with a length of 300 cm will be simulated by applying a lightning current impulse into the tower. As the next part, the Marx generator will be modified to generate a standard lightning impulse voltage with a superimposition of oscillations. In order to generate such impulses, the damping resistors of the Marx generator have to be replaced by a set of inductors and resistors in series. The third part deals with the measurement of the breakdown voltage on a rod-rod electrode configuration with different air gaps and frequencies. A cumulative distribution function of the breakdown voltage and the voltage-time curve will be extracted for each case. As the last step, the measurement results will be compared with the breakdown characteristic of the standard lightning impulse voltage: The higher the frequency of the oscillation, the voltage-time curves comes nearer to the standard impulse voltage, which is caused by a higher damping at higher frequencies. Moreover, an oscillated lightning impulse voltage has a higher crest value of the breakdown voltage in comparison to the standard lightning impulse voltage, because of the overshoot of the voltage shape.