Hydro One - System Information

System Information

Hydro One's Transmission Line voltages are 500,000 volts, 230,000 volts and 115,000 volts. Hydro One has interconnections with Manitoba Hydro, Hydro-Québec, Minnesota Power, Detroit Edison/ITC, Niagara Mohawk Power and the New York Power Authority.

Generators Hydro One works with the Transmission and Distribution network by connecting Hydro One’s generating facilities to them. They deliver the electricity they generate at hydroelectric, coal, natural gas, wind, solar and nuclear facilities to businesses and people across Ontario. The generator has different responsibilities than Hydro One. The transmission generators connected to Hydro One’s high voltage system are connected at more than 50 kV (50,000 volts). The transmission-connected generators are registered with the Independent Electricity System Operator (IESO). Transmission lines, strung between metal towers or concrete poles, are not as plentiful as their distribution lines, which are most commonly strung between wooden poles. The distribution system is connected to Hydro One’s generating facilities. They deliver the electricity they generate at hydroelectric, wind and other facilities to businesses and people across Ontario. These distribution felicities work at voltages of 50 kV or less.

Ontario's electricity grid is made up of a 29 000 km high-voltage transmission network that delivers electricity to large industrial customers and municipal utilities and 123 000 km low-voltage distribution system that serves about 1.3 million end use customers mainly in rural service areas along with smaller municipal communities in the province. To date more than75 percent in the applications to connect small generators are in Hydro One's rural service territory along the companys distribution system. While Hydro One has connected thousands of small projects to the grid they are approaching their technical limits of the wires and equipment in some rural locations. In these areas there are two issues that limit the number of projects that Hydro One can safely connect without putting the grid in jeopardy. The first issue is the physical limits of the power lines and the second is a phenomenon called islanding. In larger areas that are densely populated, Hydro One's wires are thicker and designed to deliver lager amounts of electricity. In rural areas, Hydro One's distribution wires are smaller, thinner and deliver a smaller amount of electricity because they were designed to serve a much smaller amount of customers than in large urban centers. These thinner lines deliver electricity safely and reliably to rural customers and are able to support the connection of small generation projects spread across the line, but these lines become over loaded when we try to feed more electricity back to the grid then the line was built to deliver. In some areas where the program is extremely popular, many generators want to connect to the same thin line but the line is not able to support the transfer of so much electricity.

The second issue is about islanding. Hydro One's distribution system knows how to protect itself under certain conditions. For instance, during a storm is a tree falls on a line the system shuts itself down similar to a circuit breaker. This protects the company's customers and employees from accidentally coming into contact with a live electrical line, it also protects appliances like televisions from uncontrolled surges and drops in voltage. In addition, when there is a fault the line needs to be dead. Also when solar panels are attached to such lines they must also be shut down when there is a fault on the line. If they are not shut down, electricity keeps flowing from the solar panels to all points between the panels. This can create an unsafe condition called islanding, which can potentiall put customers, employees, and the equipment drawing power from that line at risk. Right now Hydro One prevents islanding by limiting the amount of generation that the company connects in one area, this ensures that the electrical load is greater than generation at all times. Ontario has moved to smart meters, which could support even more solutions to these problems, by using the company's existing network and working with customers, Hydro One is exploring new ways to deliver the cleaner electricity which Ontarians are helping to generate.