  In this paper, we propose an AC power flow based cascading failure model that
explicitly considers external weather conditions, extreme temperatures in
particular, and evaluates the impact of extreme temperature on the initiation
and propagation of cascading blackouts. Specifically, load and dynamic line
rating changes are modeled due to temperature disturbance, the probabilities
for transmission line and generator outages are evaluated, and the timing for
each type of events is carefully calculated to decide the actual event
sequence. It should be emphasized that the correlated events, in the advent of
external temperature changes, could together contribute to voltage instability.
Besides, we model undervoltage load shedding and operator re-dispatch as
control strategies for preventing the propagation of cascading failures. The
effectiveness of the proposed model is verified by simulation results on the
RTS-96 3-area system and it is found that temperature disturbances can lead to
correlated load change and line/generator tripping, which together will greatly
increase the risk of cascading and voltage instability. Critical temperature
change, critical area with temperature disturbance, identification of most
vulnerable buses, and comparison of different control strategies are also
carefully investigated.
