Abstract
Evaluation of attractive areas of high- and ultra-high voltage power transmission lines to direct lightning strokes is based on modeling of propagating progress of the lightning leader approaching the transmission line. The aim of the modeling is to determine the effectiveness of lightning protection for a given line design. The statistical models are currently being developed to extend the conventional deterministic models by embracing the randomness of the discharge channel in space and hence to reproduce the statistical distribution of the striking points. These models require experimental data for understanding of the lightning leader development process and to validate the model across the measurement data. This paper reports on the measured trajectories of discharge channels of long laboratory sparks in various high voltage laboratory arrangements. The sparks were initiated by switching and lightning impulses with peak values ranging from 1200 kV to 3364 kV of positive and negative polarity for two types of high-voltage electrode systems (sphere-sphere and sphere-plane), arranged at distances of 3.3 m and 5.5 m from each other. Statistical distributions of angles describing trajectory of discharge channels in space are reported for a total number of 540 recorded discharges. The results can serve as reference measurement data to develop and evaluate the accuracy of simulation models incorporating statistical nature of the lightning leader development process.
Highlights
Development of power transmission lines has currently reached Ultra High Voltage (UHV) level as high as 1100 kV AC and ±800 kV DC being put into commercial operation in China since 2009 and 2010 respectively, and currently going further towards ±1100 kV
Development of transmission grids requires estimations of lightning performance of transmission overhead lines to determine the effectiveness of lightning protection for a given line design
The shielding failures are reported as the main cause of the tripouts of the ultra-high voltage (UHV) lines and contribute significantly to the trip-outs of high voltage lines
Summary
Development of power transmission lines has currently reached Ultra High Voltage (UHV) level as high as 1100 kV AC and ±800 kV DC being put into commercial operation in China since 2009 and 2010 respectively, and currently going further towards ±1100 kV. The UHV transmission requires extremely high towers of overhead lines exceeding 100 m heights, with large spans between live conductors, tower structures and protection wires. Due to the large distancing between live and earthed parts of the lines and equipment, the ratio between rated voltage and the insulation co-ordination withstand-voltage levels has been significantly decreased with the increase of the rated voltage (as per IEC Std. 60071-1 [2]). The extensive dimensions of the UHV tower structures make their attractive areas to lightning extremely high, causing a serious threat of shielding failures due to the direct lightning strokes to the lines. According to statistical analyses on lightning performance of transmission lines, the shielding failures are the main cause of the trip-outs of the UHV lines [3]
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