There have been a lot of scare stories in the media about electrical power grids in recent times, suggesting that it would be a simple matter to bring down a national transmission system by way of a minor cyber attack or physical sabotage - thereby bringing that nation's infrastructure to a grinding halt.
There's just one problem with that idea: it's "a bunch of hooey," according to power-engineering boffin Seth Blumsack.
Blumsack and his colleagues were moved to look into the matter of deliberate power-grid crashing after recent papers and studies in hefty journals - including some briefed to US politicians - painted a grim picture earlier this year. The perception was that making a targeted strike on a relatively minor electrical installation such as a neighbourhood substation (by bomb, arson or electronic/network sabotage) could easily bring down the whole grid to which it was attached.
According to Blumsack and his fellow 'leccy boffins Eduardo Cotilla-Sanchez and Ed Hines, the alarmist analyses are based on a particular type of mathematical modelling of power grids - so-called "topological" models.
"Some modellers have gotten so fascinated with these abstract networks that they've ignored the physics of how things actually work," Hines says.
"This can lead you grossly astray."
Blumsack, Hines and Cotilla-Sanchez decided to contrast the performance of a topological model with one based on actual physics - specifically on Ohm's and Kirchoff's Laws governing the flow of electricity in the real world. They tried out both kinds of model on an accurate representation of the North American Eastern Interconnect, the largest and one of the most trouble-prone portions of the US grid, using real-world data from a test case generated in 2005.
The three engineers say that the physics-driven model was much closer to reality, and that this verifies what physics models show. The results showed that in fact it is major grid components through which a lot of power flows - big generating stations and massive transformers - which are the main points of vulnerability, not the minor installations scattered across the country.
It isn't so much that a minor event on a minor line or installation can't crash the network: such things do happen. But in general there have to be huge numbers of such minor events before one of them happens to hit the miracle weak point and bring everything down. It would be an impossible task for terrorists or other malefactors to know in advance just where and when a minor pinprick could cause massive effects.
"Our system is quite robust to small things failing," says Hines.
Hitting a bigger installation or link, which would generally be better secured and more resilient, would be much more likely to work. Even then a well-resourced terror or sabotage unit with the ability to knock out bigger grid components would struggle to take down the whole thing as it is still very difficult to know exactly where and when to strike.
"It takes an incredible amount of information," says Hines, "to really figure out how to make the grid fail."
Hines and his colleagues' paper, Do topological models provide good information about electricity infrastructure vulnerability?, is published here by the journal Chaos. ®