Resilience-Driven Strategic Grid Planning with an Overload Protection Scheme Reducing Cascading Outages

State-of-the-art strategic grid planning processes are concerned with fulfilling the requirements of normal grid operation as well as performance under disturbances such as (n-1)-failures and selected exceptional contingencies. In order to ensure grid security, it becomes important to also consider events of low probability but the high impact in the grid planning stage. In this paper, the ability of power systems to deal with high-impact events and to perform under circumstances beyond what is considered in normal planning principles, specifically, the performance under multiple faults happening in close temporal proximity, is investigated. Since it is not reasonable to design a grid for (n-x)-security in general, the focus is not to avoid interruptions during extreme events altogether, but to exploit existing flexibilities in handling the consequences and to consider them in strategic grid planning in order to reduce their impact. This work, therefore, outlines a framework for resilience consideration by introducing an optimized overload protection scheme that can reduce cascading outages and load loss caused by initial double faults. In the second step, this scheme is included in a strategic grid planning optimization. Study case results based on a realistic high voltage grid show that a significant reduction in double-fault cases with 20% or higher load loss can be observed using the introduced scheme in the grid planning optimization.