  Distribution grid reliability and resilience has become a major topic of
concern for utilities and their regulators. In particular, with the increase in
severity of extreme events, utilities are considering major investments in
distribution grid assets to mitigate the damage of highly impactful outages.
Communicating the overall economic and risk-mitigation benefits of these
investments to regulators is an important element of the approval process.
Today, industry reliability and resilience planning practices are based largely
on methods that do not take explicit account of risk. This paper proposes a
practical method for identifying optimal combinations of investments in new
line segments and storage devices while considering the balance between the
risk associated with high impact low probability events and the reliability
related to routine failures. We show that this method can be scaled to address
large scale networks and demonstrate its benefits using a Target Feeder from
the Commonwealth Edison Reliability Program.
