A long term target of global guerrillas in our emerging war, will be the large infrastructure networks that our national economy relies upon (as do all modern developed economies). The most critical and complex network is our power grid which contains over 1 m kilometers of high-voltage power lines between 115 -765 kVs. The network can be further subdivided into the following:
- 1,633 generator nodes.
- 2,179 disribution substation nodes.
- 10,287 transmission substation nodes.
In recent paper, "Structural Vulnerability of the North American Power Grid," Reka Albert (et. al.) analyzed the vulnerability of the power grid based on modern techniques (see "Cascading System Failure" for more on the vulnerability of scale free networks). The key to this analysis is to find those nodes that serve as "hubs" for the network. The hubs, if taken out during an attack, have the greatest likelihood to disrupt the network and create a cascade of failure. They found the following:
- Highly connected nodes are a mix. Power engineering principles correctly suggest that the majority of highly connected nodes will be power plants (see "Design Flaws: Methods of Attacking Critical Infrastructure" for more). However, contrary to expectations, a small number of transmission substation nodes serve are also highly connected -- 50 have a degree higher than 10.
- 1% of the transmission substations are high load nodes. These high load substations are nodes with high betweeness (a high load of shortest paths between nodes on the network). These substations aren't necessarily highly connected nodes and some are merely high load throughput for long-haul connectivity (a critical part of the US power grid since 50% of the electricity generated is allocated via the wholesale market, much of it over long distances due to NIMBY restrictions on local power production). High load nodes are best termed the "hubs" of the network.
- 900 of the distribution substations can potentially become isolated clusters (41% of the total). This means that these substations are only lightly connected to the grid. If the transmission substation that connects them is taken off-line via an attack, they are disconnected from power generation and go dark.
Methods of Attack
This research indicates the potential success of different modes of global guerrilla attack against a modern power grid:
- Attacks on power substations and their direct connectivity will have little impact. The high degree of redundancy at the power substation level prevents major system failure. This is in stark contrast to the simple, production limited system in Iraq (see "Iraq: Electricity Disruption" for more) where the removal of a power plant from the grid will have a major impact. A big caveat on this "finding" is: this analysis doesn't account for "base power" generation from large producers (hydro-electric and nuclear). Power production isn't homogeneous. The elimination of these large systems from the grid would result in major disruption.
- Attacks on transmission substations yields the greatest system impact. In general, the removal of high load substations is more important than highly connected substations. A loss of only 4% of the highest load transmission hubs disconnects 60% of the grid from power.
- Cascading failures can amplify the impact of high-load node removal. Cascading failure can shut down 60% of the grid with the removal of only 2% of the high-load nodes. If 1% are removed, 40% of the grid goes dark. I suspect that better analysis based on sorting the high-load nodes by the quality of their connections (based on voltage, with the high quality nodes as those with the largest number of high voltage connections) would radically reduce the number of failed nodes needed for a system-wide cascade.
End Note: The implication is that an carefully prepared simultaneous attack against 10-20 substations of the right type could take 60% of the US end-users offline for an extended period (potentially weeks). If exploited by additional well planned attacks, this damage could be extended indefinitely.
The solution to all of this type of vulnerability, isn't a complete rework of the grid. Instead, it's a resilient community. A community that produces most of what it needs locally.