Home › Ontario's Electricity Market › Understanding the Electricity Market › Generation, Transmission and Distribution › Transmitters › System Overview

System Overview

The diagram below illustrates how the transmission system in Ontario works and what distribution takes place between power generation and power consumption.


 

1.  Generating station:

large nuclear, coal, gas and renewable

2.   Step-up transformer:

allows the power to travel a long way

3.  Transmission line:

long-distance 500/230 kilovolt (kV) lines

4.  Step-down transformer:

allows the power to be divided up

5.   Transmission lines:

shorter-distance 115 kV lines

6.  Step-down transformer:

distributes the power

7.  Distribution lines:

local 27.6 and 13.8 kV lines

8.  Electricity:

enters your home at 120 or 240 volts.

Transmission assets include the following.

  • The network consists of common-use facilities that serve all customers. An example would be a facility that transports electricity from a large source of generation and interconnects with neighbouring areas.
     
  • Line connections move electricity to end users. These are the transmission lines that connect the various towers and transformer stations.
     
  • Transformation connections either:
    • "step down" electricity distribution to a level that is less than
      50 kilovolts and send it to a transmission substation, or
    • "step up" electricity from a generating station to transmission lines.