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Fragility and Risk Analysis of Electrical Substation Equipment Using Reliability and Endurance Time Methods

Delaviz Bonab, Arman | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53811 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Esmail Pourestekanchi, Homayoon
  7. Abstract:
  8. Electrical substations and its vital components such as switchgears, have experienced severe damage during recent earthquakes, followed by widespread blackouts around the world. To improve the seismic resiliency of power grids and use probabilistic decision-making frameworks, comprehensive fragility data for the different equipment is needed. The purpose of this study is to assess the vulnerability of equipment in substations and to develop fragility curves for this equipment. For this purpose, four main equipment of switchgear, namely circuit breaker, disconnect switch, current transformer and surge arrester, have been modeled in three dimensions and verified. After examining the different failure modes and determining the dominant failure mode, the fragility of the equipment have been evaluated both in the stand-alone and connected to the adjacent equipment conditions. To evaluate the effect of the characteristics and content of input seismic excitation on the fragility of this equipment, four sets of ground motions with different content have been used. It was observed that the fragility of the equipment is affected by earthquake characteristics such as site soil type and distance from fault and pulse of earthquake velocity. The effects of dynamic interaction between equipment have been assessed using two types of connectors and the fragility of the equipment in the connected state has been developed and compared with the fragility of the equipment in the stand-alone state. It is concluded that considering the interaction between the equipment has a significant effect on the vulnerability of the equipment and the effect of both types of connectors on the response and fragility of the connected equipment is not the same. Next, two-variable fragility functions in terms of maximum ground acceleration and maximum ground velocity have been developed to evaluate more reliable seismic vulnerability for connected equipment. In addition, the effect of modeling uncertainties on the fragility of these apparatuses has been investigated and it was observed that if modeling uncertainties are not taken into account, the average annual failure rate for all equipment is estimated to be unrealistic and low. Also, by performing sensitivity analysis, the effective variables in the seismic response of the connected equipment have been determined. In this thesis, using Endurance Time method, as a method with lower computational cost, and by presenting a new approach, response distribution and fragility curve with considering record-to-record variability and uncertainty in modeling parameters were estimated and the results are compared with the results of conventional methods. In the final chapter, ET method is used to analyze the equipment risk inside the reliability methods to reduce the computational cost
  9. Keywords:
  10. Electrical Substation Equipment ; Reliability Model ; Endurance Time Method ; Modeling Uncertainty ; Dynamic Interaction ; Vulnerability Analysis ; Fragility Curve

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