The power grid may determine whether we can kick our carbon habit

Minutes before 4 p.m. on a sizzling September day two years ago, right at the time when they were most needed, San Diego's air conditioners suddenly died. Thousands of television and computer screens also flickered into darkness. Stoplights stopped working, gas stations ceased pumping, and traffic slowed to a snarl. Trains ground to a halt and planes idled on the runway. Wastewater treatment pumps shut down, spewing some 4 million gallons of raw sewage into the Pacific. Around 2.7 million "customers" -- amounting to anywhere from 5 to 7 million people -- lost their power, with some remaining in darkness for 12 hours or more.

As commuters extricated themselves from highway gridlock, and batteries faded away on millions of electronic devices, folks flocked to the handful of neighborhood bars that –– thanks to generators –– were able to keep their lights and refrigeration going. There, they could drink away the darkness and speculate as to what had caused this sudden plague of electrical impotence.

Many assumed it was terrorism -- San Onofre Nuclear Generating Station had been sabotaged, they said, or the North Koreans had set off an electromagnetic pulse that fried the grid, or maybe an Iranian cyberattack had crippled the computers that keep the modern world humming. Others blamed solar flares for disrupting the cosmic electromagnetic field, or suggested that a more earthly storm had caused distant wind farms to go haywire. Then again, perhaps a raven just landed on the wrong piece of equipment out in the desert and got fried, its death rattle reverberating through the transmission lines all the way to San Diego.

Their guesses weren't stupid or outlandish -- they all involved genuine threats to the power grid. But the biggest power outage to hit the Western Grid in a decade actually started hundreds of miles east, at a substation outside Yuma, Ariz. And it began not with a bang, but with a misplaced checkmark that ultimately crashed Southern California's electrical system.

That event was no freak occurrence. It could have happened anywhere, at any time, in the complex machine that generates, transports and delivers power to nearly every corner of the nation. Our proliferating air conditioners and gadgets have put new pressures on the grid, as the demand for electricity has grown twice as fast as the infrastructure needed to carry that power. Now we're straining it even more by trying to get that power from cleaner, more fickle sources. Meanwhile, the electrical grid -- the circulation system of today's modern age -- is still stuck back in the '80s, like one of those guys from high school who clings to a mullet haircut and his Dungeons and Dragons dice. Compared with what's to come, some say, San Diego's blackout might seem in retrospect no more than an excuse for a candlelit block party.

A 6-foot-high, gleaming white cross stands alongside a mostly empty road near Tonapah, Ariz. At its foot is a tiny Nativity scene, and an angel on the end of a stick. The shrine's purpose isn't clear, but its location makes it seem like an altar dedicated to the patron saint of electricity. Behind it, rising from the desert scrub, are the elongated containment domes of Palo Verde Nuclear Generating Station's three reactors. And beyond them lie two huge fields of photovoltaic panels and three natural gas power plants. There is probably no other five-square-mile patch on the planet with more electrical generating capacity.

Yet just as critical is the network of transformers, switches and wires through which all that electricity flows. Congregated just north of Palo Verde, a dozen high voltage transmission lines slice the sky, crackling ominously as they link up in the giant, skeletal "switchyard." The lines, gently curving toward earth between each giant tower, lead inward and outward in every direction, like spokes on a bicycle wheel, making the Palo Verde/Hassayampa switchyard the biggest power-trading hub and crossroads in the region -- the electrical Union Station of the West.

Among these lines is the 500-kilovolt Hassayampa-North Gila, or H-NG, line. On Sept. 8, 2011, about 1,300 megawatts -- almost half of all the electricity imported into Southern California that day, enough to power about 1.5 million homes -- flowed westward through the H-NG line. All that juice was needed because it was so hot; the mercury hit 115 degrees in El Centro, and even sea breeze-cooled Oceanside reached 88. By mid-afternoon, air conditioners cranked across the Southwest, while irrigation pumps pushed water onto the half-wilting lettuce in California's Imperial Valley.

On its way to San Diego, the H-NG line passes through the North Gila substation outside of Yuma. Just before 2:00 that afternoon, Arizona Public Service, the substation's operator, sent a technician out to fix a capacitor bank, used to stabilize voltage in long-distance lines. As he worked -- we'll call him Kilo Watt, since the utility has kept his or her identity secret -- he marked each completed step on a checklist to make sure that he didn't miss anything. But then Watt, distracted, put a mark in the wrong place, causing him to skip one critical step: bypassing all that juice around the capacitor bank so that he could work on it safely.

At approximately 3:27 p.m., he cranked open the disconnect switch, an event that should have been uneventful. Instead, the 500 kilovolts still running through the line began to arc -- the current leaping through the air, much the way the evil Emperor zapped Luke Skywalker in Return of the Jedi. Watt continued cranking the switch, hoping to manually break the arc. Instead, the writhing electrical serpent grew larger, and some 43 milliseconds later, the entire H-NG line "tripped," like a home circuit breaker, and shut down.

The chain reaction, which would climax just 11 minutes later, had begun.

But the roots of the San Diego blackout are deeper than that Yuma substation. In order to really understand what happened, we need to travel back in time to the grid's primordial days among the hardrock mines of the Rocky Mountains.

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