The figure below is the example of a system overload. If we were to follow Pt.
A along the plot above, as the load increases as indicated by the number of lights that are on,
load voltage drops.
Should this continue, voltage would decline below normal operational
parameters.
This will eventually lead to "voltage collapse", where the entire
power system would fail, and all the lights turn off. This point of "voltage
collapse" in the above diagram occurs at the nose of the power-voltage
(PV) curve.
It is possible that this condition of "voltage collapse" may
also occur due to a loss of a transmission line caused by an component
failure.
As mentioned earlier we have taken certain liberties to create idealistic
scenarios. Due to the complexity of voltage dynamics, "voltage collapse"
may actually occur earlier than at the nose of the PV curve as shown below.
