July 6 (Bloomberg) -- An Ontario judge barred striking electricity distribution workers from blocking access to government-owned power plants as the province struggles to meet demand in a heat wave.

About 1,000 employees of Hydro One Inc., members of the Society of Energy Professionals, have been on strike since June 1 and are picketing power suppliers. They forced Ontario Power Generation Inc. to shut down six of eight generating units at its coal-fired Nanticoke plant on June 24, reducing its output by 3,000 megawatts. Power shortages have made it necessary to import electricity, pushing up costs, officials say.

Superior Court Judge Colin Campbell said workers must have access to all power plants.

``There is a unity to the system,'' Campbell said at a hearing in Toronto today. ``I'm satisfied there is a risk to the system as a whole.''

The unionized Hydro One workers are on strike because they oppose a wage and benefit plan proposed by the company that would pay younger workers less than older ones.

Hydro One operates the system that carries electricity throughout the province from dozens of power plants. Campbell delayed a decision on a request for the same protection from another supplier, Bruce Power LP, Canada's biggest nuclear complex, pending a hearing next week.

The union has a constitutional right to picket and inform people about the issues in the strike, Kate Hughes, a lawyer representing the union, told the judge.

``I'm not outlawing picketing,'' Campbell said. ``Far from that.''

No Blocking Cars

He rejected a proposal to allow picketers to temporarily prevent cars from entering plants, a common strike tactic, saying even a five-minute delay per car would create long lines and affect plant operations.

Ontario Power is the government-owned utility that generates 70 percent of the electricity in the province from 34 hydroelectric .plants, five coal-fired plants and three nuclear plants. It has sued the union to recover the revenue lost from plant shutdowns caused by picketers.

Power disruptions blamed on the strikers by the utility have occurred as southern Ontario endures a heat wave. Temperatures reached as high as 34 degrees Celsius (93 degrees Fahrenheit) on June 28, straining the power system as people used their air conditioners.

The province reached record summer power consumption June 27 with demand peaking at 26,157 megawatts, according to the Independent Electricity System Operator, which monitors Ontario's power supply.

Imported Power

The extra demand and forced shutdowns boosted imports of expensive electricity from the U.S., pushing up the average cost in June to 7.12 cents a kilowatt, 42 percent higher than the government-set rate of 5 cents that homeowners pay for the first 750 kilowatts that they use.

Temperatures in southern Ontario cooled today to 22 degrees Celsius at noon in Toronto. They're forecast to rise into the 30s by the weekend.

The case is Ontario Power Generation Inc. v. Society of Energy Professionals, 05-cv-292353 PD 3, Ontario Superior Court (Toronto).

To contact the reporter on this story: Joe Schneider in Toronto at jschneider5@bloomberg.net.

Last Updated: July 6, 2005 14:37 EDT