August 15, 2003

READER BROCK CUSICK emails that power is back on on Wall Street, as of just a few minutes ago. News reports still say Manhattan is largely without power, though. Here's the latest from the Times, and here's the Globe story.

Meanwhile reader Herbert Jacobi has some thoughts on what this means:

First I am a retired Electrical Engineer with 30 years in the power business.

Here is a site for a map of the North American Grid:
Link

Note the difference between the east and west grids. It doesn¹t really matter concerning this outage but it does when one talks about updating the nation's grid.

Second re Gorman's dissertation: Cough up your $500 and you can buy a map or CD of the nation¹s grid (and more seriously) the natural gas pipeline infrastructure here: Link

Security. The critical security point is the substations and actually there isn¹t much you can do.

The real vulnerability is the physical security. Generating plants usually have armed guards so while everyone talks about them they aren¹t the major problem and the security there could be upgraded fairly easily. People also worry about the transmission line. The lines cover to much territory to be protected, though passive sensors might make sense. However as shown each time there is an ice storm or hurricane it's shown they can be repaired rather quickly. Without a map (If you don¹t have your $500) it still wouldn't be hard to just follow the power lines (they are kind of visible) to their terminus points. That¹s where the security is seriously lacking. Anyone who knows what they are doing could cause major damage and long term blackouts very easily. And you wouldn¹t need any explosives, special tools, or even a gun.

The other area of vulnerability is the change in the relays. They use to be electromechanical and while there are still tens of thousands of those out there since the early 1980¹s the trend has been to microprocessor based relays. These can be connected to a phone line and communicated with via a computer network. I am willing to bet that most of them still have the factory default passwords on them and of those that have been changed the new passwords are probably simple mnemonics. The damage wouldn¹t be major or long lasting but it could be done from a foreign country and be hard to trace.

The recent blackout.

While (since I'm retired and out of the business) I don¹t have any more info then you have here are some speculations.

The eastern grid and specificly the connections between Canada and the US have some very big lines Not only 500KV but 750KV. These are good for wheeling a lot of power but when they trip the power has to go elsewhere, instantaneously, When lightning hits a line a relay opens the line in a very short time. Most relays on large lines operate in less then a cycle (60 cycles @ second so each cycle is about 1/16th of a second or about 16ms. The breakers take about two cycles to open. They can reclose in about 20 to 40 cycles because of various physical factors. If it¹s a SLG (single line to ground) fault the line opens and usually automatically recloses. However if it¹s a multiphase fault then the line will lock out until an operator closes it. This can be done remotely via SCADA. I don¹t know how the companies operate but this is fairly standard. There has been speculation that simultaneous lightning strikes can cause multiple outages. Remember the power has to go elsewhere instantaneously. This can cause other lines to overload and then that causes other lines to overload and so on.

It could also be a relay failure. The last few blackouts in the US (both east and west) have been caused by a relay failing to operate or operating in a way it shouldn¹t. It wouldn¹t surprise me if this is the cause here also. The new relays are so complicated that it¹s easy to make a mistake and set something you shouldn¹t. In the old days you had to know how to set the relay. Now you have to not only do that but know what not to set.

Interesting. The main lesson I take from it is to get a backup generator. . . .