Cascade failure is a type of failure that occurs in interconnected systems like electricity grids. In such an event, the failure of one or more parts trigger the breakdown of many interconnected parts or the entire network itself. The recent power blackout in Pakistan is being attributed to such a failure. A technical issue at the Guddu Thermal Power Plant caused the frequency in the grid to drop to 0 Hz from the normal 49.5 Hz in one second. This led to a cascade of failures and the safety systems shut themselves down to prevent further damage.