Evaluation of power substation equipment seismic vulnerability by multivariate fragility analysis: A case study on a 420 kV circuit breaker

Recent earthquakes have shown that Electrical Power Substations apparatuses are seismically vulnerable. This causes to disrupt the power supply in many cases, and therefore their seismic evaluation with high reliability is significantly important. Using fragility curves is a common practice for assessing seismic vulnerability. In general, fragility curves are based on only one intensity measure (IM), such as peak ground acceleration (PGA). This study has attempted to propose multivariate fragility analysis. One of the major advantages of this developed multivariate fragility analysis is to more reliably determine the seismic vulnerability of a region. A 420kV circuit breaker (CB) was modeled and analyzed by using finite element technique. The results show that by adding another IM as peak ground velocity (PGV) the dispersion of the created data decreases to a great extent and therefore, the developed fragility surfaces helps conducting the seismic risk evaluation of electric power system components with higher level of reliability. Based on the obtained numerical results it can be expressed that for moderate damage state the fragility values are not much dependent on the PGV variation, while for severe damage state the dependence of fragility values on PGV is noticeable, particularly for PGA values in range of 0.1–0.7g.