IEEE Power & Energy Magazine - July/August 2020 - 52

This exemplifies the fact that one enhancement solution may be
preferred from a reliability perspective, while, from a resilience
perspective, other options may be more attractive.
of the parameter a), and the "budget" indicates the number
of available investment options allowed as a proxy for their
total cost (e.g., budgets equal to one, three, and five mean
that up to one, three, and five investment decisions can be
made, respectively). The figure shows the most economical
option (a budget equal to one) is to invest in an HVdc link
connected point to point between the Atacama Desert
(node 4) and Santiago (node 29). In fact, this enhancement
option features two main characteristics.
First, pre- and postfault power flows are fully dispatchable due to power electronics equipment that allows system
operators to have a higher level of controllability of the power
flows, co-optimizing them with other operational measures,
e.g., generation (re)dispatch, the exercise of reserve services,
and so forth. The second characteristic is the unique topological connection of this candidate link, which bypasses
most substations between the north and the center of the
country, reducing, in this way, its exposure to earthquakes
(note that the main impact from earthquakes is on substation
equipment rather than towers and transmission lines).
In fact, empirical evidence from past events in Chile
strongly suggests that substations (rather than lines) experience the most severe problems during earthquakes. For
example, in the 8.8-Mw earthquake in 2010, only three
towers failed, while 12 (out of 46) substations in high-voltage transmission systems showed some level of damage. For
this very same reason, the best complements for this HVdc

link are the hardening of substations supplying Santiago,
i.e., Alto Jahuel and Cerro Navia (a budget equal to three).
Interestingly, for a budget equal to five, two storage facilities, each a pumped-hydro storage unit of 300 MW, are added
to the optimal portfolio. In this case, the storage facilities
located in Cumbre and Lagunas allow the system operator to
more efficiently manage the large amounts of renewable generation located in the north (under any outage conditions, with
and without earthquakes), whose production is transferred
through the HVdc link to the central area of the country in
Santiago, which is, in turn, supplied by the Cerro Navia and
Alto Jahuel substations (among others). All of the aforementioned assets are part of the selected portfolio solution, clearly
indicating the value of coordinated investment. These five
enhancement options selected as a unified portfolio thus act
as one synergic multiasset enhancement, providing the best
feasible insurance to the main system load center against the
occurrence of large earthquakes.

Summary and the Way Forward

CEENS (GWh)

In the context of the transition from reliable to resilient power
grids, we have demonstrated the need for considering riskbased (rather than average) indicators to identify the necessary
enhancements in network and system infrastructure. Importantly, in this article, we discussed some of the fundamental
differences among various investment solutions (e.g., redundancy and substation hardening) compared to more flexible
operational solutions, with the overall aim of improving the reliability and resilience of power grids.
Base
Case
Although the proposed mathemati48
cal framework used to determine
46
HVdc Link
resilience network enhancements is
44
fully probabilistic, this differs from
HVdc Link
42
the classical probabilistic-based
Substations Alto Jahuel and Cerro Navia
40
decision-making models due to the
HVdc Link
explicit incorporation of risk aver38
Substations Alto Jahuel and Cerro Navia
sion, in contrast to the risk-neutral
Storage in Lagunas and Cumbre
36
attitude assumed in classical reli34
ability studies. We argue that plan32
ning for resilience corresponds to
becoming risk averse so that the
30
0
1
2
3
4
5
resulting network designs are less
Budget
exposed to HILP events in comparison to designs resulting from
(risk neutral or even simply risk
figure 10. The optimal portfolio solutions for resilience enhancement for different
unaware) reliability studies.
budgets. CEENS: conditional EENS.
52

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