Field tests: Performances of practical earthing systems under lightning impulses

In this paper, experimental test set and test results on the performance of practical earthing systems under high impulse currents are presented where the earthing systems consist of 3 earthing systems configurations, 2, 3 and 4 rod electrodes. Calibration tests using linear test load in order to validate the transducers adopted for this study are also discussed in this paper. This paper also presents the selection of the remote earth and some data from previously published work of the same site and earthing systems configurations under low magnitude currents and at power frequency. Soil ionisation characteristics on the real earthing systems were investigated. The performance of earthing systems are investigated based on its voltage and current shapes, earth pre- and post-ionisation resistance values and time delays. It was found that under impulse conditions, earthing systems behave differently where the earth resistance was found to be non-linear which are due to thermal and ionisation processes.

► We investigate the performance of 2, 3 and 4 simple earthing systems at power frequency and transients.
► Experimental test set up was calibrated and validated using high voltage standard techniques.
► Earth resistance values are found to be lower under transients than that at power frequency.
► By understanding this behaviour, optimum design of earthing systems can be achieved in future.