An experimental study on the seismic interaction of flexible conductors with electrical substation equipment

Flexible conductors are usually employed to interconnect equipment items in electrical substations located on seismically active regions. They have sufficient slack, which allows the conductor to accommodate the relative displacement of the interconnected equipment under seismic loading. Generally, in the design process of the interconnected equipment and their connections to the flexible conductors, the seismic behavior of the conductors is not considered and the dynamic forces generated by them during an earthquake event are not taken into account. However, these forces could be significant and could overload the equipment and cause damage. This thesis presents an investigation on the seismic behavior of a class of high voltage flexible conductors by evaluating their interaction with and their effect on the equipment to which they are connected. This was done by performing various experimental tests on one of the most commonly used configurations of flexible conductors in substations throughout the province of British Columbia in Canada. The experiments included a quasi-static test on the full-scale flexible conductor and four series of shake table tests on the large scale models of the equipment in their stand-alone or interconnected set-up. The design of the equivalent models of the equipment was based on the stiffness and the natural frequencies of the actual equipment obtained from field tests. The input signals for the shake table were synthetic earthquakes. Three records from earthquakes in California were modified to fit the IEEE (the Institute of Electrical and Electronics Engineers) and BC Hydro prescribed design spectra. The specimens were instrumented throughout with acceleration and displacement transducers. Two multi-axial load cells were employed to measure the loads generated at the connections of the conductor to the equivalent equipment during the tests. The test results are summarized and presented in various forms. Various analyses including spectral analysis is performed on the test results and comparisons are made between the results of various tests and various analyses. This investigation showed that the dynamic effect of the flexible conductors should be considered while evaluating the seismic capacity of the interconnected equipment.