MURPHY'S LAW AND OTHER POINTS

In the early morning of February 1, when the temperature was 11 below zero (F), an electric power substation in southeast Denver exploded in flames and left a 36-square-mile area with some 300,000 people without power.

Why did it have to happen just on such a bitterly cold day? Murphy's Law, parrot the parrots.

But Murphy's Law is nonsense. If the two events are independent, then by definition the probability of one remains unaffected by the occurrence of the other; on the other hand, if they are dependent, their joint occurrence is explained by their dependence, and not by Murphy's "Law."

For example, a substation (in essence a big transformer stepping down the high-voltage power transmitted from the power plant to low-voltage power for distribution to consumers) is unlikely to explode if it lies idly in the sun; bridges do not collapse when nothing is crossing them; and cables do not snap when they are not loaded. Equipment is more likely to fail when it is stressed. A transformer is under greater mechanical and electrical stress when it transforms more power and becomes more vulnerable as it approaches its power rating; it will very probably fail when that rating is exceeded. Stress and failure are dependent events.

The precise details of failure in the Denver transformer are not yet known, but it is highly likely that it was caused by the high demand for power due to the cold, and not by the malice of nature that the coincidences by Murphy's Law tacitly assume.

And there are other lessons in this incident.

Within half an hour, power was restored to 240,000 people, and to the rest within about 6 hours. (The blaze itself was put out in 3 hours, and without injuries.) A civilized society with central power sources is resilient; a commune with piddling amounts of energy from expensive toys is an unviable utopia.

While a quarter of a million people were without heat or light, worried about their water pipes freezing, or in monumental traffic jams (no traffic signals), they had the chance to ponder Ralph Nader's exhortation to "disconnect from the utilities." If there were any who were not ecstatic about the idea, it served the blockheads right: they should have taken Lovins' advice of using conservation as an energy source. Besides, had they been smart enough to spend some $20,000 on photovoltaics, they could have basked in the heat radiated by several light bulbs.

But we are headed for another story, concerning the liquid insulators with which large transformers are rifled.

"It originally was feared that polychlorinated biphenyls, a toxic substance suspected to be cancer causing and often found in power transformers, might be involved," cooed an AP dispatch. "But officials later said that the transformer contained mineral oil, not PCB's."

Another AP dispatch reported that the EPA had found 8 per million (EPA limit is 50 ppm) of PCB. The Boulder Daily Camera, a heavily censored "news" paper that caters to the enlightened avantguarde of a college town second only to Berkeley, gave this report a headline stretching over four columns: PCBs RELEASED IN DENVER SUBSTATION FIRE.

Few people have ever heard of PCBs or their history, and that suits the censors: it is only the ignorant who can be duped.