MA: small fixes, add simulation/modeling blurb

1 files changed, 28 insertions, 18 deletions

diff --git a/ma/safety_reset.tex b/ma/safety_reset.tex
index c5dd90d..8aa31bf 100644
--- a/ma/safety_reset.tex
+++ b/ma/safety_reset.tex
@@ -310,20 +310,30 @@ that can consume a good fraction of a gigawatt all on their own.
 
 \subsection{Operational concerns}
 \subsubsection{Modelling the electrical grid}
-% FIXME
-
-\subsubsection{Generator controls}
-% FIXME
-
-\subsubsection{Load shedding}
-% FIXME
-
-\subsubsection{System stability}
-% FIXME
-
-\subsubsection{Power System Stabilizers}
-% FIXME
 
+Modelling performs an important role in the engineering of a reliable power infrastructure. The grid is a complex,
+highly dynamic system. To maintain operational parameters such as voltage in various parts of the grid, grid frequency
+and currents inside their specified ranges complex control systems are necessary. To design and parametrize such control
+systems simulations are a valuable tool.  Using model calculations the effects of control systems on operational
+variables such as transmission efficiency or generation losses can be estimated. Model simulations can be used to
+identify structural issues such as potential points of congestion. The same models can then be used to engineer
+solutions to such issues, e.g.\ by simulating the effect of a new transmission line.
+
+There are several aspects under which the grid or parts of the grid can be simulated. There are static analysis methods
+such as modal analysis that yield information on electromechanical oscillations by computing the eigenvalues of a
+large system of differential equations describing the collective behavior of all components of the grid. Modal analysis
+is one example of simulations used in grid planning. Using modal analysis likely oscillatory modes can be identified and
+ultimately these results can inform a decision to install additional stabilization systems in a particular location.
+In contrast to static analysis, transient simulations calculate an approximation of the time-domain behavior of some
+variable of interest under a given model. Transient simulations are used e.g.\ in the design of control systems.
+Power flow equations describe the flow of electrical energy throughout the network from generator to load. Numerical
+solutions these equations are used to optimize control parameters to increase overall efficiency.
+
+% TODO decide what of this to keep.
+% \subsubsection{Generator controls}
+% \subsubsection{Load shedding}
+% \subsubsection{System stability}
+% \subsubsection{Power System Stabilizers}
 
 \section{Smart meter technology}
 
@@ -339,9 +349,9 @@ is automatically disconnected until they pay their bill are significantly aided
 controlled and monitored remotely. A remotely controllable load switch can also be used to coerce customers in
 situations where that was not previously economically possible\footnote{
     The swiss association of electrical utility companies in sec.\ 7.2 par.\ (2)a of their 2010 whitepaper on the
-    introduction of smart metering\cite{vseaes01} cynically writes that remotely controllable load switches lead a new
-    tenant to swiftly register with the utility company. Mysteriously, this whitepaper completely vanished from their
-    website some time after publication. Luckily for us, the internet archive had a copy.
+    introduction of smart metering\cite{vseaes01} cynically writes that remotely controllable load switches ``lead a new
+    tenant to swiftly register'' with the utility company. This whitepaper completely vanished from their website some
+    time after publication, but the internet archive has a copy.
 }.
 
 To the customer the utility of a smart meter is largely limited to the convenience of being able to read it without
@@ -1087,8 +1097,8 @@ hundreds of local systems each with autonomous goverance.
 Despite the awesome complexity of large power grids the physics underlying their response to changes in load and
 generation is surprisingly simple. Individual machines (loads and generators) can be approximated by a small number of
 differential equations and the entire grid can be modelled by aggregating these approximations into a large system of
-linear differential equations. Evaluating these systems it has been found that in large power grids small-signal
-steady-state changes in generation/consumption power balance cause a linear change in
+nonlinear differential equations. Evaluating these systems it has been found that in large power grids small-signal
+steady-state changes in generation/consumption power balance cause an approximately linear change in
 frequency\cite{kundur01,crastan03,entsoe02,entsoe04}. \emph{Small signal} here describes changes in power balance that
 are small compared to overall grid power.  \emph{Steady state} describes changes over a timeframe of multiple cycles as
 opposed to transient events that only last a few milliseconds.