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A survey was undertaken on the current assessment and refurbishment practices of North American utilities regarding substation grounding systems. The information was gathered using standard survey techniques where all interested parties were requested to fill out a short written survey and return it with the understanding that their responses would be kept anonymous. Survey results show that almost all utilities evaluate the integrity of their ground grids at some point, and have maintenance or engineering standards for determining the integrity. Test equipment is frequently used to evaluate integrity, and ground grids not meeting these standards are commonly upgraded. The results also show that most use high resistivity surfacing material, yet very few test the resistivity of the material at the time it is installed. This paper provides guidance on the recommended best practices based on these survey results, which can be used for benchmarking purposes. It also includes a short discussion on the importance of maintaining the substation grounding system.

Due to failures of interconnected equipment in recent earthquakes, it is suspected that the seismic interaction of the flexible conductors with the equipment during a strong ground motion could cause additional unpredicted forces, resulting in damage or collapse of the equipment they interconnect. This paper presents the results of an investigation into the dynamic behavior of flexible conductors by performing several shake table tests on a class of flexible conductors and the relevant 500-kV interconnected equipment used in substations throughout the province of British Columbia in Canada. The test specimen consisted of large scale models of the equipment items and the actual size flexible conductors. The shake table input records were synthetic earthquakes generated to fit an IEEE prescribed response spectrum. This investigation showed that the dynamic effect of flexible conductors must be considered when evaluating the seismic capacity of interconnected equipment.

Prompted by recent failures in earthquakes of interconnected high-voltage electrical equipment in substations and a lack of available design information, BC Hydro initiated an experimental program to address this issue. Powertech Labs, in collaboration with BC Hydro and the University of British Columbia (UBC), formulated a research plan to investigate how flexible conductors affect the seismic response of interconnected substation equipment. This paper describes the result of static tests on flexible conductors and of calculations of dynamic properties of equipment in BC Hydro substations. For a set of six interconnected configurations the natural frequencies were calculated and where possible, calibrated to the measured natural frequencies of the equipment.