  Extreme events represent a challenge to natural as well as man-made systems.
For critical infrastructure like power grids, we need to understand their
resilience against large disturbances. Recently, new measures of the resilience
of dynamical systems have been developed in the complex system literature.
Basin stability and survivability respectively assess the asymptotic and
transient behavior of a system when subjected to arbitrary, localized but large
perturbations. To employ these methods to assess the resilience of power grids,
we need to choose a model of the power grid. So far the most popular model that
has been studied is the classical swing equation model for the frequency
response of generators and motors. In this paper we study a more sophisticated
model of synchronous machines that also takes voltage dynamics into account,
and compare it to the previously studied model. This model has been found to
give an accurate picture of the long term evolution of synchronous machines in
the engineering literature for post fault studies. We find evidence that some
stable fix points of the swing equation become unstable when we add voltage
dynamics. If this occurs the asymptotic behavior of the system can be
dramatically altered, and basin stability estimates obtained with the swing
equation can be dramatically wrong. We also find that the survivability does
not change significantly when taking the voltage dynamics into account.
Further, the limit cycle type asymptotic behaviour is strongly correlated with
transient voltages that violate typical operational voltage bounds. Thus,
transient voltage bounds are dominated by transient frequency bounds and play
no large role for realistic parameters.
