Editing Cascading failure (section)

== In power transmission ==

Cascading failure is common in [[power grid]]s when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system.  Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements.  Cascading failure is a common effect seen in [[high voltage]] systems, where a [[single point of failure]] (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time.

This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer.

Monitoring the operation of a system, in [[real-time computing|real-time]], and judicious disconnection of parts can help stop a cascade.  Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures.<ref name="chao">{{cite arXiv |last1=Zhai |first1=Chao |title=Modeling and Identification of Worst-Case Cascading Failures in Power Systems |eprint=1703.05232 |class=cs.SY |year=2017}}</ref>

One of the primary problems with preventing electrical grid failures is that the speed of the control signal is no faster than the speed of the propagating power overload, i.e. since both the control signal and the electrical power are moving at the same speed, it is not possible to isolate the outage by sending a warning ahead to isolate the element.

=== Examples ===
Cascading failure caused the following [[power outage]]s:
* [[Northeast blackout of 1965|Blackout in Northeast America in 1965]]
* [[1999 Southern Brazil blackout|Blackout in Southern Brazil in 1999]]
* [[Northeast blackout of 2003|Blackout in Northeast America in 2003]]
* [[2003 Italy blackout|Blackout in Italy in 2003]]
* [[2003 London blackout|Blackout in London in 2003]]
* [[2006 European blackout|European Blackout in 2006]]
* [[2012 northern India power grid failure|Blackout in Northern India in 2012]]
* [[2016 South Australian blackout|Blackout in South Australia in 2016]]
* [[2019 Argentina, Paraguay and Uruguay blackout|Blackout in southeast South America in 2019]]
* [[2025 Chile blackout|Blackout in Chile in 2025]]
* [[2025 European power outage|Blackout in Spain, Portugal and France in 2025]]