Investigating Protection Challenges on Distribution Systems Self-Healing

Due to its radial characteristic, distribution networks are susceptible to de-energizing many customers during an outage event. Through distribution network reconfiguration (DNR) techniques, self-healing (SH) provides a solution to partially or entirely restore impacted customers. However, the SH approach must change the network configuration to restore customers within minutes after the fault occurs. The need for speed does not allow the full consideration of other network aspects, such as protection settings and how relays will be impacted after the restoration process. This paper analyzes and discusses the impacts of active distribution networks (ADN) SH on protection performance. The approach is based on considering the network power flow and fault levels before and after the restoration to analyze how the predefined protection settings respond to the new configuration. A standard distribution network is used for the approach validation, where a protection study is developed, and a Mixed-Integer Linear Programming (MILP) formulation for SH is proposed. The results present optimal restoration for different fault locations and which protection elements would have tripped in each relay after the restoration.