Firefighters work to extinguish a fire in a transformer in Toronto.Tim Fraser
Maintaining an electricity grid is akin to managing traffic lights in a busy road network to keep vehicles moving - in this case, at close to the speed of light - while having no control over the number of automobiles that want access to the roads.
The transformer station is a crucial link in the grid system, converting high-voltage electricity of up to 765,000 volts coming from transmission lines to lower voltage in a step-down series that reduces it to the 120-volt level that can be brought into homes. It works like a series of off-ramps and arterial roads from a superhighway, eventually leading to your residential street.
On hot days, the transformers are vulnerable to overheating because they must operate continually at peak capacity while absorbing outside heat. The wires also heat up, adding to the stress. Some utilities have even been reported to hose down transformers to cool them, says Pierre Guimond, president of the Canadian Electricity Association.
When a transformer blows, two sets of customers are affected: those whose power comes directly through that piece of equipment, and those whose service is interrupted as engineers manage the disruption to the grid. The Ontario grid is managed by the Independent Electricity System Operator, which co-ordinates the efforts of power supplies; Hydro One, which is the high-voltage transmission company; and local distribution utilities such as Toronto Hydro. Throughout the system, breakers are tripped to ensure the sudden absence of power does not destroy other equipment. Engineers first look to reroute power to other stations, in the way a traffic co-ordinator would look for alternative routes around an accident.
Engineers' most crucial job is preventing "cascading blackouts" that can occur because of the inter-connectedness of the system. In 2003, a tree crashing into a wire in Ohio caused a blackout that extended from Ontario through the northeastern United States as far as New York City. Hydro One and the Independent Electricity System Operator have invested in additional switches and other barriers that prevent damage from migrating through the system.
A report on the 2003 event - North America's most extensive blackout - led to a revamping of the North American Electric Reliability Corp., which oversees all members of the interconnected, continent-wide grid system. The corporation now publishes mandatory reliability standards, covering everything from the age of parts and equipment to information-technology management procedures. It can fine member transmission companies for noncompliance.
In Ontario, one of the major changes since 2003 has been the introduction of natural-gas-fired power generation, which gives the system far more flexibility at meeting peak loads compared to coal and nuclear plants. The geographic distribution of the so-called "peaker" plants also provide greater flexibility to the transmission system when there is a major accident, such as a fire at a transmission station.
The April, 2004, report on the Northeast blackout stressed the need for transmission companies and other participants in the grid to update their equipment constantly, noting the system was largely constructed a generation ago to serve a far more centralized power system. Now, different power supplies are getting access to the grid.
However, getting parts can be a problem. Manufacturers have largely moved out of North America, closer to boom markets in Asia and Eastern Europe, Mr. Guimond says. "We're all queuing up" for crucial equipment, he said.