The impact of current-carrying bus decentration and inclination on impulse current measurement by large size Rogowski coils

In order to obtain the waveform of lightning current, the Rogowski coil is installed directly on tall structures such as the UHV transmission line towers. However, the measured results are influenced by the structure involved. This paper investigates the effects of different current-carrying bus positions to the large size Rogowski coil on the measured results. Two different large size coils´ frequency spectrum characteristics are analyzed and the effects of coil parameters on frequency band are also discussed. The impact of current-carrying bus decentration and inclination the Rogowski coil measured results is investigated. Both calculation and test strategy study methods are employed for the impact investigation. It is shown that the decentration of current-carrying bus has little impact of less than 4% errors on the measurement results when the current-carrying bus´s decentration distance changed from 0 cm to 30 cm. The inclination of the current carrying-bus has more significant impact on the measured results. The error of measured current amplitude changes from 1.17% to 7.4% whilst the inclination angle changes from 0°to 60°under 5kA impulse current, and from 1.5% to 17.9% under 10kA impulse current. The theoretical analysis is in accordance with the experimental results. It is suggested that the Rogowski coil should be located installed perpendicular to the current-carrying bus and the decentration impact is ignorable when the decentration distance is less then 20% of the coil radius.