Seismic retrofitting of an HV circuit breaker using base isolation with wire ropes. Part 1: Preliminary tests and analyses

Seismic retrofitting of an HV circuit breaker using base isolation with wire ropes. Part 2: Shaking-table test validation

“…In this section, the design of a shaking-table test campaign, which was performed on a base-isolated 380 kV circuit breaker and was previously numerically analysed in [7], is illustrated. This circuit breaker was qualified according to CEI EN 266271-207 standard for a seismic level AF2.5.…”

“…Because of the linearity of the material, the moment is proportional to the deformation by a coefficient that was calibrated during a cyclic-test campaign [7]. The measures provided by other strain gauges, which were applied at the base of the interruption chambers (S3) and the base of the supporting structure, were directly converted into stress using the values of the elastic modulus of the two materials, which were either known (steel) or were evaluated by executing tests on single components (ceramic).…”

“…Three of the nine accelerograms that were used in the preliminary analysis [7] were selected as the input for the shaking-table tests. In the selection, the maximum allowable displacement of the shaking-table (±100 mm) was considered by applying a highpass filter to the records using a cut-off frequency of 0.35 Hz to avoid affecting the response of the isolated apparatus, whose natural frequency is approximately 0.5 Hz.…”

“…The experimental results confirmed that wire-ropes are suitable for the base isolation for electrical equipment. In a companion paper [7], the preliminary analysis and design of this base isolation system was reported, and the effectiveness in reducing the seismic response of a 380 kV circuit breaker was demonstrated using numerical analysis with simplified models, which were calibrated through a series of experimental tests on ceramic components and joints. Based on the CEI EN 62271-207 [2] standard, which requires the seismic qualification verification of HV electrical components by conducting dynamic tests, in this work, the results of a shaking-table campaign to test the base-isolated 380 kV circuit breaker are illustrated.…”

A Parallel Model for Predicting the Horizontal Dynamic Behavior of Helical Wire Rope Isolators

“…These metal devices, also adopted for the seismic protection of light but costly equipment [2] and high voltage ceramic circuit breakers [3], [4], [5], [6], [7], have been recently used as vertical isolation bearings in the antiseismic basements developed specifically for the base isolation of the two statues known as "Bronzes of Riace", located at the Archaeological Museum of Reggio Calabria, Italy [8]. Shaking table tests performed at the Department of Structures for Engineering and Architecture of the University of Naples Federico II (Italy) on a scaled structure, seismically isolated using four curved surface sliders and four wire rope isolators, have shown that the latter can be strongly useful when the complete recentering of the base-isolated structure is required and when the displacements of the base isolation system have to be reduced [9].…”