IEEE Power & Energy Magazine - July/August 2017 - 88

history

Andrew Isaacs

simulation technology
the evolution of power system modeling

In 1915, Nature magazIne published a short paper, "The principle of
Similitude." The author, nobel-prizewinning physicist John Strutt, Lord
Rayleigh, introduced his paper by stating, "I have often been impressed by the
scanty attention paid even by original
workers in physics to the great principle
of similitude." He went on to propose
many examples of physical behavior that
could be easily predicted through an existing understanding of similar physical
phenomena. The principle of similarity
he referred to has, in recent years, been
important in the field of fluid dynamics,
where the consideration of scale models
must be analogous not only in shape to
their real-world counterparts but in their
dynamic interactions with surrounding
media over time.
engineers in every field continually
strive to make models to better predict
actual outcomes. For power systems engineers, models are critical to the planning and economic design of the massive
infrastructure that keeps our lights on.
In the beginning, it was all about mathematics. mathematics, initially aided
by slide rules, became digital. With the
help of computers, it remains the core
of almost all system simulations. but
physical modeling has always had a role
as well, the boundaries of which were,
from the earliest days, stretched by usDigital Object Identifier 10.1109/MPe.2017.2690527
Date of publication: 16 June 2017

ieee power & energy magazine

ing the laws of similitude to use more
convenient frequency, impedance base,
and physical size.
Today's power systems engineers are
equipped with tools that harness incredible computing resources to model every aspect of the power grid. In a single
simulation, tens of thousands of power
transmission lines are connected with
their respective substations, including
representations of power producers and
consumers, and all the equipment needed to support the system. These tools
can calculate the effect in Southern California when a hydro plant is tripped in
Washington State and determine whether a new photovoltaic solar plant in
arizona will exceed stability limits on
critical transmission paths. Thousands
of possible line and generator outages
can be automatically simulated to determine whether any one outage could
result in a loss of power to consumers.
Other types of simulation programs
are able to zoom into the details of the
complex control firmware of a wind turbine and predict whether the machine
will respond correctly if a serious electrical system event occurs nearby. The
individual power electronic components
within a massive high-voltage (HV) dc
terminal can be modeled along with
all their controls to provide engineers
with crucial design feedback, ensuring
everything works when it is first energized. The traveling wave of current
from a lightning bolt can be shown to
1540-7977/17©2017IEEE

arc across a tower, echo through a substation, and be safely dissipated into
protective equipment. These tools and
others help power system planners and
equipment designers optimize their designs and most importantly ensure that
our complex electric network continues
to operate reliably and efficiently.
Simulation technology notwith standing, changes in the power system
landscape are straining our ability to
understand and predict potential impacts
before we construct equipment. The
industry is responding quickly to these
needs. The future of simulation technology is seemingly unlimited as simulation tools, aided by rapid advances in
computing technology, keep pace with
new demands. To better understand the
nature and importance of power simulation tools, it is worthwhile to review
their history, assess where we are now,
and imagine how new tools will evolve
to address tomorrow's system design and
performance challenges.

Pen and Paper: Early
Power Systems Planning
The original electric power systems were
essentially metropolitan distribution systems. extensive networks did not yet exist as feeders extended radially from
local generating stations. network calculations for voltage and current were
made manually. Instability between two
or more local generators was not yet an
issue as few generating plants operated
july/august 2017

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