۱- Introduction

۲- Method

۳- Numerical modeling of equipment and conductors

۴- Analysis

۵- Results and discussion

۶- Failure probability evaluation

۷- Conclusions

References

Abstract

The present paper studies the impact of dynamic interaction between high-voltage substation equipment on the response and vulnerability of substation equipment. The 3D numerical model is developed for four types of vulnerable equipment in the both unconnected and connected conditions. The bus slider-rigid bus assembly is utilized to establish the connection between the equipment. The incremental dynamic analysis is carried out in the developed systems to produce the fragility function for each equipment. Also, the Monte Carlo approach is employed to evaluate the accuracy of the generated functions. It is concluded that the incorporation of connection parts in the model can significantly alter the fragility of equipment and the relative performance of vulnerable equipment. Moreover, it is found that when more than two equipment are connected, the effect of indirectly connected equipment can be neglected if the contribution of higher modes to its response is small. The fragility functions for which the interaction effects are accounted can be used to reliably assess the seismic risk of substations.

Introduction

Electrical substations are the nodes of power transmission network which their continuous operation after earthquakes has paramount importance for the well-being of community. The damage of earthquake to substations may impose disruption in rescue operation after the earthquake and in the performance of other critical lifelines such as water delivery systems. Substations are composed of various types of equipment such as surge arrester (SA), current transformer (CT), circuit breaker (CB), disconnect switch (DS), etc., which are connected through the conductors. Most equipment include slender ceramic insulators under a large concentrated mass, which increases the vulnerability to the earthquake-induced forces [1–۳]. Moreover, conductors result in the interaction between the equipment with different dynamic characteristic, which in turn can contribute to their vulnerability [4]. Also, as the voltage level of substation is increased, the fragility of its component is increased accordingly. The interconnection between the equipment are provided through the rigid bus assemblies or flexible cables as conductor. Rigid buses include an aluminum pipe with a flexible connector at one end. Two types of common connectors are the flexible strap connector (FSC) and bus slider (BS). Although connectors are originally designed for the thermal expansion purposes, they increase the flexibility and dissipation capacity of conductors, which may lead to the reduction in the adverse interaction effects. However, the transfer of force between equipment, variations of dynamic properties and exceedance of connectors’ displacement limit may cause severe interaction effects. Depending on the slack, cables may increase or decrease the response of equipment. Thus, the interconnected equipment has become a complex dynamic system.