Study backs Hydro One's small generator connection limits

Monday, March 26, 2012

by DAVE PINK

A third-party study has validated the Hydro One policy of limiting the electricity generated from private solar generators in some parts of the province to either seven or 10 per cent of the total electrical load carried on the utility’s power lines.

The study by Kinectrics Inc. concluded that the Hydro One practice was “prudent and reasonable,” for safety reasons. The practice is intended to prevent what engineers call “islanding,” a situation where a portion of the power system that has become disconnected is unintentionally energized, posing a threat to the repair crews and the general public.

“As we are connecting private generators we have to keep safety and reliability in mind,” Ayesha Sabouda, Hydro One’s manager of generation connections, said during a recent news conference to announce the release of the Kinectrics study.

The restrictions had been criticized by advocates for the increased use of privately generated sustainable energy and by rural landowners anxious to take advantage of the province’s Feed-in Tariff (FIT) and microFIT programs, but were denied access to the system because of overcapacity.

The Kinectrics study confirmed that in some parts of the province the existing electrical system can take up to 10 per cent private generation without fear of islanding, while in other areas the system can take only seven per cent without danger. This study recommends a much more detailed analysis of the province’s power distribution system to determine what changes should be made to improve the system’s capacity to take privately generated electricity. “Kinectrics recommends maintaining the existing anti-islanding constraints until appropriate studies and tests aimed at establishing new quantifiable anti-islanding limits are completed,” the report’s executive summary concludes.

That will take time and money, said Sadouda, who said it would be unreasonably expensive to expect the provincial power distribution utility to begin a rapid update of its system, considering that much of the system is newer and does not yet need replacing.

However, she said gradual improvements will be made as they are needed. “We look at our assets and replace them when necessary. It’s an ongoing process. We don’t want to replace assets that we don’t have to,” said Sabouda.

“We’re moving forward with a number of studies,” she added. “My feeling is that we’d like to be able to connect more generators, but it is always a process of continual improvement.

“There are some hard technical limits. That’s just one of the realities.”

Hydro One points out that, as of March 20, more than 8,275 microFIT generators have been linked to the system and provide 72,000 kilowatts of power, enough for 25,000 homes.  Another 3,258 generators have been approved and are moving forward. BF