High-current impulse experiments were performed on volcanic ash samples to determine the magnetic effects that may result from the occurrence of volcanic lightning during explosive eruptions. Pseudo-ash was manufactured through milling and sieving of eruptive deposits with different bulk compositions and mineral contents. By comparing pre- and post-experimental samples, it was found that the saturation (i.e., maximum possible) magnetization increased, and coercivity (i.e., ability to withstand demagnetization) decreased. The increase in saturation magnetization was greater for compositionally evolved samples compared to more primitive samples subjected to equivalent currents. Changes in remanent (i.e., residual) magnetization do not correlate with composition, and show wide variability. Variations in magnetic properties were generally more significant when samples were subjected to higher peak currents as higher currents affect a greater proportion of the subjected sample. The electrons introduced by the current impulse cause reduction and devolatilization of the ash grains, changing their structural, mineralogical, and magnetic properties.

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Porcelain insulators have a long history and wide application range in power systems, but just like any other insulator, they can fail. A number of pole fires occurred on lines utilising porcelain suspension insulators. In some cases, the insulators appeared to be visually intact with no external signs of degradation or abnormal stress. This prompted a comprehensive assessment to identify the mechanism that leads to the permanent loss of insulating properties while retaining external physical characteristics. A single test is not sufficient to determine the underlying cause of conduction as results may produce contradictory conclusions. Electrical tests were able to identify samples with poor dielectric strength. Nevertheless, these same samples exhibited excellent mechanical properties. Despite successfully passing numerous porosity tests, scanning electron microscopic analysis revealed porosity and multiple microscopic punctures in the porcelain dielectric. Only upon complete dissection of samples, the conduction mechanism was revealed. This article discusses the challenges associated with establishing the root failure mechanism for the investigated porcelain insulators that allows visually sound samples to lose their insulating properties without experiencing catastrophic failure.