• Eastern Alberta DC Transmission Line
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DC Lines

Transmission Options
Power can be transmitted using either alternating current (AC) or direct current (DC). All modern power systems use AC to generate and deliver electricity to customers through transmission lines and then through distribution lines to where it is needed. The technology now exists to use DC for bulk power transmission. AC electricity is converted to DC electricity for transmission and then converted back to AC electricity for distribution to customers on the AC power grid. A converter station at each end of the line is required to convert power from AC to DC and back so we can use the power in our homes, farms and businesses.

In Canada, DC transmission lines are in operation in Manitoba and Quebec and have been used in many places throughout the world for decades. ATCO Electric has owned and operated a “back-to-back” converter station on the Saskatchewan border since 1989. (Power is converted from AC to DC and back again in the same station. Direct AC connections to the Saskatchewan power grid are not possible because their system frequency is not synchronized with Alberta’s.)


The Benefits of DC
DC transmission lines can transmit power more efficiently than AC transmission lines and require a smaller right-of-way.


Energy Efficiency
DC lines experience lower line losses than AC lines. When electric current moves through the conductors of a transmission line some of the power is lost in the form of heat. Transmission conductors offer less resistance to DC, meaning less power is wasted.


Minimize Land Use Impact
A DC transmission line uses less land than an AC transmission system of equivalent capacity. One 500 kilovolt (kV) DC line can transport a similar amount of power as a double-circuit 500 kV AC line, two single-circuit 500 kV AC lines, or four double-circuit 240 kV AC lines. A comparison between the rights-of-way is shown in the diagram to the right.