PrintThe PJM Network Failure
Let's look at a real-life example of what can go wrong. The following excerpt, describing a PJM Network failure, was taken from a July, 2010, National Geographic Magazine article. PJM Interconnection is the regional transmission organization that coordinates the movement of wholesale electricity in all or parts of 13 eastern states and the District of Columbia.
August 14, 2003. Most of PJM's network escaped the disaster, which started near Cleveland. The day was hot; the air conditioners were humming. Shortly after 1 p.m EDT, on August 14, 2003, grid operators at First Energy, the regional utility, called power plants to plead for more volts. At 1:36 p.m. on the shore of Lake Erie, a power station whose operator had just promised to "push it to my max max" responded by crashing. Electricity surged into northern Ohio from elsewhere to take up the slack.
At 3:05 a 345-kilovolt transmission line near the town of Walton Hills picked that moment to short out on a tree that hadn't been trimmed. That failure diverted electricity onto other lines, overloading and overheating them. One by one, like firecrackers, those lines sagged, touched trees, and short-circuited.
Grid operators have a term for this: "cascading failures." The First Energy operators couldn't see the cascade coming because an alarm system had also failed. At 4:06 a final line failure sent the cascade to the East Coast. With no place to park their electricity, 265 power plants shut down. The largest blackout in North American history descended on 50 million people in eight states and Ontario.
At the Consolidated Edison control center in lower Manhattan, operators remember that afternoon well. Normally the power load there dips gradually, minute by minute, as workers in the city turn off their lights and computers and head home. Instead, at 4? p.m. lights went out in the control room itself. The operators thought: 9/11. Then the phone rang, and it was the New York Stock Exchange. "What's going on?" someone asked. The operators knew at once that the outage was citywide.
There was no stock trading then, no banking, and no manufacturing; restaurants closed, workers were idled, and everyone just sat on the stoops of their apartment buildings. It took a day and a half to get power back, one feeder and substation at a time. The blackout cost six billion dollars. It also alarmed Pentagon and Homeland Security officials. They fear the grid is indeed vulnerable to terrorist attack, not just to untrimmed trees.
Full text available at National Geographic.
Since 1990, electric demand has increased by about 25 percent, while expansion of existing transmission infrastructure has decreased by about 30 percent over this same time period. While annual investment in new transmission facilities has generally declined or been stagnant during the last 30 years, substantial investment in generation, transmission, and distribution are expected over the next two decades. Both industry and government estimate that electric utility investment needs could be as much as $1.5 to $2 trillion by 2030. Some progress in grid reinforcement has been made since 2005, but public and government opposition, difficult permitting processes, and environmental requirements are often restricting the much-needed modernization.
In a congestion study prepared by the U.S. Department of Energy, congested transmission paths now affect many parts of the grid across the country. One recent estimate concludes that power outages and power quality disturbances cost the economy between $25 billion and $180 billion annually. These costs could soar if outages or disturbances become more frequent or longer in duration. There are also operational problems in maintaining voltage levels. Again, an excerpt from the National Geographic Magazine article shows just how little tolerance there is in maintaining a reliable voltage in the system:
PJM engineers try to keep the current alternating at a frequency of precisely 60 hertz. As demand increases, the frequency drops, and if it drops below 59.95 hertz, PJM sends a message to power plants asking for more output. If the frequency increases above 60.05 hertz, they ask the plants to reduce output. It sounds simple, but keeping your balance on a tightrope might sound simple too until you try it. In the case of the grid, small events not under the control of the operators can quickly knock down the whole system.Full text available at National Geographic.
Many new transmission lines have been proposed to either alleviate congested paths or to provide redundancy so that existing portions of the transmission system can be temporarily taken out of service for proper maintenance and modernization. In many cases, funding is not the primary reason why these critical lines are not being built. Overly stringent permitting requirements, lawsuits, and other regulatory issues often inhibit transmission line construction.
Just as high voltage transmission needs have increased, so has the need to increases distribution. Distribution includes the system of substations, wires, poles, metering, and billing involved in delivering electricity to the consumer. The need to expand the distribution infrastructure and install new distribution equipment to meet population and demand growth will require continued investment. It is estimated that electric companies will spend $14 billion per year on average over the next 10 years on distribution investment. Over the next decade, distribution investment is likely to exceed capital spending on generation capacity as well.