Characterisation of earth electrodes subjected to impulse and variable frequency currents

Summary

The evaluation of the lightning response of earthing systems is important for the design of overvoltage protection of power systems and for ensuring electrical safety of personnel. The response is affected by many factors including the impulse shape and magnitude, the geometry and extent of the earthing system as well as the physical properties of the soil medium. In this work, controlled field tests of a 1.2m vertical ground rod has been carried out with both low voltage impulse and variable frequency energisations using a concentric ring current return arrangement to encourage uniform current distribution around the test electrode. The electrode potential is measured with respect to a remote earth reference. The frequency responses of the tested electrodes are determined from measured voltages and currents obtained from the swept variable frequency tests. The frequency response of the tested electrodes is computed by numerical simulation using detailed models of the test setup that include variation in permittivity and resistivity values. The experimental and simulated results are then compared. Finally, the same electrode is tested using a high voltage impulse generator to compare the response under higher magnitudes of current.

Additional informations

Authors

Zhou Xuan, Zeng Rong, Zhuang Chijie, Wang Zezhong, Chen She, Plesa Ilona, Anaca Octavian