IEEE Power & Energy Magazine - November/December 2017 - 25

We bring together examples from Europe, North America,
and Australia to identify five indisputable facts about
planning and operating modern power systems.
compounded by the rise of wind and solar generation. Competitive pressures from wind and solar generation are pushing many thermal plants to retire, thereby further reducing
the frequency response of the system. These challenges
are most evident in the contributing activities preceding a
blackout that occurred in South Australia during an extreme
weather event in September 2016; they also highlight the
need for reform on frequency control arrangements.
Initial responses to the South Australia blackout indicate
that a variety of capabilities are available for natural gas generation and renewable generators that could have been used to
arrest or minimize the cascading failure experienced during
the storm, which included tornados and caused fallen transmission towers. The key issue facing Australia's regulators
now is figuring out how to value resources that provide services contributing to grid reliability when penetration levels
are more than 75% of demand.

Fact Two: Geographic and
Resource Diversity Provide
Additional Reliability to the System

arose during the energy crisis of the 1970s in the United States.
At that time, the concern was that international disputes regarding oil and gas could negatively impact the electricity, industrial, and transportation sectors. As a result, the U.S. Congress
passed the Power Plant and Industrial Fuel Use Act of 1978 to
reduce power plant reliance on international fuel sources. Then,
as now, resource diversity was considered a key strategy to mitigate risk and manage costs. These strategies continue to show
value for modern power systems.
Under current system conditions, wind and solar generation
increases resource diversity. They reduce reliance on fossil-fuel
resources and can provide alternative sources of generation
when hydropower systems are faced with extreme conditions;
however, they are subject to their own diversity challenges.
Compared to traditional resources, for which weather challenges (e.g., hurricanes, flooding, and extreme cold) are infrequent, wind and solar resources that are concentrated in one
area experience a variety of seasonal, diurnal, and weatherrelated challenges.
Spatial variability of solar and wind resources differs by
region and can impact the geographic distribution required
to achieve geographic diversity within a system. Spatial variability is influenced by local and regional climates as well
as local terrain complexity. Figure 2 illustrates this point

At high penetration, renewable resources need to contribute significantly to the reliability of power systems. If power system planners
and regulators want to mitigate all risk of loss of load, the solution
is relatively straightforward: build
lots of redundant generation and
transmission. The problem with this
Jaisalmer
approach is that it is very expensive;
in addition, because electricity is a
200 km
fundamental input for the modern
economy, excessive electricity costs
that result from efforts to mitigate
all risk are financially challenging.
One generally successful approach
for reducing the costs of managDNI Correlation Coefficient
ing power system risks is to share
capacity and reserves with neigh0.68-0.75
boring regions. This approach dates
0.75-0.8
to when the first interconnections
were created in the northeastern
0.8-0.85
United States and to the creation of
0.85-0.9
the first power pools in the United
States in the 1940s.
0.9-0.95
Another risk faced by the in0.95-1
dustry relates to the overdependence on a single fuel type. A dramatic example of this challenge
figure 2. The spatial variability of DNI in India.
november/december 2017

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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2017