Electrical measurements and photgraphic acquisition of pre-discharges on long rod-rod air gaps under lightning impulse voltage

Summary

The breakdown voltage on a symmetric rod-rod electrode configuration is theoretically independent from the polarity of the electrode voltage. However, practically because of environmental and spatial circumstances (also for overhead lines), the polarity affects the breakdown voltage. Due to the constraints of measurement techniques, it had been difficult to measure the properties of pre-discharge precisely. Therefore, the breakdown process on long air gaps under lightning impulse voltages is still not investigated sufficiently. In order to investigate the breakdown process at a rod-rod configuration fundamentally, a measurement system is proposed. By means of this system, it is possible to record the electrical and photographic parameters of the breakdown process under lightning impulse voltages up to 2.4 MV. Simultaneously on both rod electrodes, the pre-discharge current is recorded in mA range up to 200 MHz. Furthermore, the pre-discharges are photographed in a nanosecond range with a high-speed iCCD (intensified charge-coupled device) camera to record the spatial development of the pre-discharges. This paper presents the measurement system in detail and reports about some measurement results in case of the positive and negative polarity of the impulse.

Additional informations

Keywords

breakdown process, high-speed camera, iCCD-camera, lightning impulse voltage, measurement system, rod electrodespre-discharge