Interties Explained: Connecting Canada’s electricity grids
By: Ryan Workman
Canadian jurisdictions want to share more electricity, but the infrastructure needed to connect power grids can be complex.
Interties link regional power grids, allowing electricity to flow between different jurisdictions, such as provinces or regional grids. As work moves ahead to further connect Canada, interties will be an essential part of infrastructure development.
What are the benefits of transferring electricity between grids?
Enabling power transmission between jurisdictions facilitates more efficient utilization of electricity, resulting in cheaper electricity.
It allows provinces to leverage each other’s comparative advantages – like low-emissions hydropower in B.C. and Manitoba, and low-cost wind and solar in Alberta and Saskatchewan. This helps smooth demand across the system while also providing additional redundancy if one jurisdiction experiences a sudden spike in demand, such as during an extreme weather event.
Both the provinces and the federal government have made announcements regarding improving electrical interties between provinces (including the provincial-territorial MOU to advance interties, and an announcement regarding the new forthcoming federal electricity strategy).
What are interties?
An intertie is a high-voltage transmission line between regional grids. Higher voltage electricity travels more efficiently.
Properties of electrical currents
Electricity is power generated by the movement of electrons between atoms. When it comes to transferring electricity, wattage and the difference between AC and DC power are two important properties to highlight.
Wattage
Power (i.e., watts), is actually a product of two sub-components, namely voltage and current.
Voltage can be thought of as comparable to pressure (i.e., the strength of the force pushing electrons through a circuit), while current can be thought of as the quantity or flow of electrons. The more current there is, and the greater the pressure, the higher the wattage. In simple terms, it’s like a household sink: voltage is your water pressure, while current is the volume of water.
Wattage is usually standardized within countries but often differs between them. For example, Canadian grids operate on 120V, while the UK uses 230V. This is why you often need a travel converter for your appliances when you travel to other countries – if the voltage is too high, it can damage electronics that aren’t designed for that much power.
DC and AC power
Sometimes, jurisdictions convert from AC (alternating current, or the kind of power used in a local grid) power to DC (direct current) power to transmit along interties, and then back to AC on the receiving end.
DC power is constant and flows in a single direction, while AC power alternates back and forth at a constant rate measured in hertz (Hz). One hertz means one back-and-forth cycle per second. In Canada, electrical grids operate at 60Hz, meaning that the flow switches back and forth 60 times per second.
Use cases for DC and AC power
When it comes to electrical grids, DC and AC power have different use cases.
AC power is the kind of power we usually utilize in a local or regional grid. This is mainly because it is easier to increase or decrease the voltage of AC power, and it is also easier to convert AC to DC. For example, the box you find on a laptop charger is an AC to DC converter. Higher voltage electricity can be transported with less energy loss, but the voltage often needs to be decreased for local use. The magnetic pulse generated by the alternating flow makes it much easier to convert AC power. AC power is also the kind of power produced by most electricity generators, though this may change as wind and solar both produce DC power.
DC power is the kind of power used in most appliances (essentially anything that uses a battery).
Long-distance transmission
Both DC and AC power have their place when it comes to long-distance power transmission.
The primary advantage of DC power is that it does not need to be synchronized. If you are transporting AC power between grids, not only does the frequency need to match (e.g., 60Hz to 60Hz), but they must also be alternating in sync. This is why the new Quebec-Maine intertie converts electricity from AC to DC, and then back to AC. DC power is also more efficient over long distances (e.g., 200-plus kilometres for overhead lines).
If you are transporting power over moderate distances between synchronized grids, AC power remains a better choice, such as with the Alberta-B.C. transmission line.
Looking ahead
As the demand for electricity continues to increase, Canada will need more resilient systems to meet that demand now and into the future. Interties will play a key role in that future as provinces look for efficient ways to share electricity and strengthen connections across Canada.
Ryan Workman is a Policy Analyst with the Canada West Foundation.