Regional seismic risk assessment method for electric power substations: a case study

In this paper, the application of risk analysis based on reliability methods to estimate the expected annual loss (repair cost) from seismic events, to substations located in the widespread area has been investigated. The proposed method is based on the PEER general framework for seismic risk assessment and using scenario sampling that generates the random annual samples of seismic events and their consequences. Probabilistic models were developed to simulate seismic hazard (including earthquake occurrence, magnitude, location and intensity), seismic response and damage of substations using fragility models and economic loss (repair cost). In seismic hazard modeling; occurrence, magnitude, depth and location of earthquake events was randomly simulated using the polynomial area source model. The intensity (PGA) of the earthquake was then calculated at the location of each substation. By collecting the existing data records from past earthquakes, the probabilistic model for the repair cost of substations was developed as a ratio of construction cost. The regional seismic risk assessment using the proposed method is implemented in an area, which includes 92 substations at the voltage levels of 63, 230, and 400 kV. The annual loss curves for substations in the case study area in both anchored and unanchored states have been estimated. The results show that the anchorage of equipment at the power substations in the study area, led to a 25% reduction in the expected annual loss. Using the difference between the average annual loss in the anchored and unanchored states of power substations, the cost of rational retrofitting of substations in the study area can be estimated.