Soaring power demand in New York, California, and Ontario over the past week forced grid authorities to institute conservation measures.

Heavy Rains Threaten Reliability in Ontario

The Independent Electricity System Operator (IESO) on Wednesday called on Toronto customers to reduce their electricity use. The grid operator that manages the reliability of Ontario’s bulk electricity system said that while significant progress had been made to restore service following severe flooding, "supply within parts of the west end of Toronto remains uncertain given the need to reconfigure the system to work around major transmission facilities that remain unavailable." The IESO said conservation was necessary "to help relieve the strain on the system."

Heavy rain in the Greater Toronto area on Monday night caused severe flooding, inundating the Richview and Manby transmission stations owned by Hydro One and cutting power to nearly a half-million customers. As of Wednesday, about 10,000 customers remained without power. As Hydro One repairs the stations, the company said there was limited need to continue with intermittent power outages; however, until the system is fully stable, the potential still existed for further intermittent outages.

NYPA Institutes Peak Reduction Program

For three consecutive days starting on Monday, the state-owned New York Power Authority (NYPA) activated a peak reduction program in response to higher power demand due to heat. The program to reduce electricity use at public facility locations in New York City calls on the Metropolitan Transportation Authority and the City University of New York to lower electricity use at 20 New York City locations during the highest-demand days. The program, which voluntarily commits customers to curtail a total of about 14 MW, can only be operated for 15 days. The duration of the reductions is limited to two to six hours, between 11 a.m. and 7 p.m.

Participating customers in the summer Peak Reduction Program reduce their electricity use with conservation measures such as shutting off unnecessary lighting and discretionary equipment. "In return for the power curtailment, NYPA pays participants $25 per kilowatt reduced, for an expected outlay that could total hundreds of thousands of dollars by summer’s end," NYPA said.

California Endures First Heat Wave Without San Onofre

The California Independent Systems Operator (CAISO) on July 2, meanwhile, urged customers for a second day to conserve energy in the northern part of the state due to an intensifying heat wave. The rare measure was issued as an unexpected outage continued at PG&E Corp.’s 1,122-MW Diablo Canyon 1 reactor, the grid operator said. The reactor’s return to service on July 2 and lower temperatures in Los Angeles alleviated the situation.

The grid hit peaks last week of nearly 45 GW on July 1 and was forecast to hit about 46 GW on July 2. CAISO’s record peak of 50.2 GW was reached in July 2006. Power prices for next-day power on July 2 delivery spiked to a five-year high but returned to normal summer levels by July 3.

The permanent closure of the two-unit San Onofre nuclear power plant has left California short on generating resources. The North American Reliability Corp. (NERC) earlier this year warned that California could face "operational challenges" from the shutdown of the reactors owned by Southern California Edison. "A prolonged and/or extreme heat wave could result in localized controlled load shedding in San Diego and Los Angeles Basin to maintain integrity of the system," NERC warned. "Several system enhancements were completed or planned to be in-service by summer peak, which should relieve some operational issues and support system flexibility during conditions of stress."

Sources: POWERnews, IESO, Hydro One, NYPA, CAISO, NERC

Sonal Patel, Senior Writer (@POWERmagazine, @sonalcpatel)