IEEE PES T&D Conference & Exposition 2022 - 123

stability is likely to become an even larger challenge. The Aug.
9, 2019, blackout in Great Britain saw a lightning strike on the
transmission system and a loss of power supply from two large
generators lead to a rapid change in frequency across the whole
system. This, in turn, triggered further instability as distributed
generation was disconnected based on protection which picks
up major frequency changes. It was reported that 1.1 million
customers were interrupted for up to 45 minutes. There were
several instances over the preceding months in which frequency
had fallen to the low end of the frequency tolerance band as well
as reductions in system inertia with lower levels of conventional
generation and more renewables on the system.
As of 2020, utility metrics do not include measurements
for distribution-level stability, but this seems a likely evolution
in the years to come. While the framework of new metrics
remains to be seen, measuring
distribution-level stability would
provide a more complete picture
of both reliability and distribution
system stability (Figure 6).
Systemwide
Technological
Advancements That
Can Help
Both utilities and regulators must
agree for customer-focused metrics
to be adopted, but once they are, the
grid will require significant updates
to improve reliability through a customer
lens. The use of advanced
switching and protection equipment
will be critical for any reliability
improvements. Fault interrupters
can be used to segment feeder lines
and automatically reroute power
when an outage occurs. This keeps
the lights on for as many people as
possible. These devices also automatically
detect whether a fault is
temporary or sustained by testing
the line with 95% less force than
conventional reclosers. These investments
and others can help build a
self-healing grid, leading to fewer
and shorter outages experienced
by customers.
Improving reliability at the
feeder level will help many customers,
but most of the outages
that play into customer experience
happen at the very edge of the grid.
When a customer lives in a location
prone to faults, such as at the edge
of the grid near an overhead distribution
transformer fuse location, it
April 2022 Show Issue
Feeder-Level
MAIFI
SAIDI and
SAIFI
Electricity
Customer
takes crews a long time to reach the area and restore power
for a small number of customers. These unnecessary field visits
cost utilities millions of dollars each year while the regular
outages are bothersome to customers. Bringing advanced faultprotection
equipment to the very edge of the grid is the best
way to help lessen the impact of these outages. Equipment like
S&C Electric Company's self-resetting interrupters can replace
conventional fuses at the grid's edge and automatically reset
following a temporary outage compared to a conventional fuse
that operates once and then needs to be manually replaced.
Conclusions
Changes in technology are driving changes in customer
expectations of power system reliability as people place
more reliance on the power grid. The electrification of other
Major
Event
Days
Commentary:
Heading toward
all outages matter
to all customers.
CEMM CEMSMI CEMI
Momentary
Interruptions
Duration of Outages
Typical
Outages 5 min
to Several Hours
CELID
Long
Interruptions
> 12 Hours
Size of Circle = Relative Level of Utility Use of This Metric
figure 5. How CEMSMI could emerge as a key index for measuring the individual
electricity user experience.
Systemwide
Feeder-Level
Electricity
Customer
MAIFI
SAIDI and
SAIFI
Major
Event
Days
Distribution
Stability?
Commentary:
Heading toward
all outages matter
to all customers and
distribution-level
stability concerns.
CEMM CEMSMI
Momentary
Interruptions
CEMI
Duration of Outages
Typical
Outages 5 min
to Several Hours
CELID
Long
Interruptions
> 12 Hours
Size of Circle = Relative Level of Utility Use of This Metric
figure 6. Distribution-level stability is a plausible future direction for reliability tracking.
ieee power & energy magazine
123
Level of Impact
Level of Impact

IEEE PES T&D Conference & Exposition 2022

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