An intertie is a connection with neighbouring electric systems that allows power to move in or out of the province. Interties provide a stable and reliable supply of electricity and are an important component of Alberta’s electric system. Primarily, they are used to import power into the province. This article below will summarize what interties are and why they’re important and matter in Alberta.
What is an intertie?
In its most basic definition, an intertie is an interconnection permitting the passage of current between two or more electric utility systems. Alberta’s transmission system currently has three interties with neighbouring jurisdictions in Saskatchewan, BC, and Montana. They are high-voltage transmission lines connecting separate regional power grids that act like bridges to allow for the import and export of electricity. This, in turn, can enhance grid stability for all of the areas involved, reliability, and affordability by balancing supply and demand across wider areas. It’s also important for integrating intermittent renewable energy sources such as wind and solar.
How do interties work?
There are a few types of connections that allow interties to function, such as AC and DC ties/lines. These connect two grids that operate at the same frequency, acting as a single, rigid synchronous system. DC are high-voltage direct current (HVDC) lines that connect two different grids, allowing them to remain independent while trading power. DC links such as these are crucial for connecting systems with different standards or when synchronizing AC systems is not feasible, and it needs to be an asynchronous system.
Interties consist of high-voltage transmission lines (often 500 kV or higher) and specialized equipment to manage voltage and frequency, such as converter stations for DC links, as an example.
Why are interties important in Alberta?
Interties are important for several reasons stated above, such as enhancing grid stability, reliability, and affordability, along with helping to manage extreme weather conditions and events by sharing resources. This is especially important for Alberta, BC, and Saskatchewan when it comes to extreme winter weather, so that other regions can send their power when local generation falls short. Essentially, they are very important for each region involved to have a more stable electrical connection in case of extreme weather or any other issue that may arise where demand is too high for the one system to run. It provides stability.
If one region has a surplus of energy, that can be passed over to another region that may be needing more on a day when they need an extra boost. In Alberta, this is important when extreme weather conditions hit, such as extreme heat or snow, and the provincial grid may need some help to stay out of the red to continue functioning without having to activate rolling brownouts or other measures.
A number of arms-length agencies oversee Alberta’s electricity system and receive their powers through the Electric Utilities Act. These include AESO (Alberta Electric System Operator), AUC (Alberta Utilities Commission), the Market Surveillance Administrator, Balancing Pool, and the Utilities Consumer Advocate. The AESO oversees the electricity system by providing for the safe, reliable, and economic operation of the Alberta Interconnected Electric System. They are tasked with providing a fair, efficient, and openly competitive market for electricity per the Fair, Efficient, and Open Competition Regulation, while the AUC ensures that the delivery of Alberta’s utility service upholds fairness and aligns with the public interest. The AUC regulates electric and water utilities and ensures that these facilities are built, operated, and decommissioned efficiently and responsibly, also providing regulatory insight into the development of projects related to Alberta’s wholesale electricity market and the retail gas and electricity markets in the province.
That is all to say that these together are also what allows the interties to exist and work within the province, all while maintaining what they do and how well they function with the current grid system in place.
Interties in Alberta
In 1986, AB and BC Hydro financed the construction of the intertie, comprised of several transmission lines which connect the two provinces’ electrical grids. In the 1990’s, Alberta deregulated its electricity market, and the prices fluctuate hourly based on demand and the available supply that is bid. The BC market has remained subject to cost-based regulation of electricity prices. Current interties in Alberta include transmission systems with connections that include Saskatchewan, BC, and Montana to the south.
The British Columbia (BC) and Alberta (AB) high voltage electrical grids are connected by a 500 kV transmission line that runs from Cranbrook, BC, to just outside Calgary, AB, along with two smaller transmission lines which cross the BC border near Sparwood and Elkford. Jointly referred to as the BC-AB Intertie.
The AESO and BC Hydro jointly operate the intertie to ensure the reliability of both electricity systems is maintained. The total transfer capacity of the intertie is 1,200 megawatts (MW), from West to East and 1,000 MW from East to West. The bidirectional nature of the intertie provides opportunities for both provinces to benefit from the import and export of electricity. As a joint facility both BC Hydro and the AESO have a role in determining how much of the total capacity is available for commercial capacity and how much is set aside for reliability margin. Typically, 80-90% of the transfer capability on interties is used for imports and exports of energy products (commercial capacity), and the remainder is held aside for inadvertent use as a reliability margin. Historically, the AESO has had a large need for reliability margin and restricted the commercial capacity on the intertie to an average of 400-600 MW (33-50%) with the remainder of capacity (50-67%) available for the reliability margin. By setting aside a margin, Alberta can rely on BC and the rest of the western grid to instantly respond with increased energy flows in the event of a sudden loss of generation. Typically, reliability margins are provided between jurisdictions without compensation.
Recently, the Alberta electricity generation mix has transitioned from largely coal-fired to natural gas, solar, and wind generation, comprising the majority of the province’s generation. Under normal operating conditions, both imports from and exports to BC are fundamental to maintaining the supply-demand balance in Alberta. For example, when intermittent renewables like solar and wind are not available, the AESO may not have sufficient electricity available to meet provincial demand.
When the MATL connected to the Alberta system, BC’s flow limit into AB was reduced by the same amount that was permitted to flow into Alberta from Montana. Until recently, this has kept the import capability typically in the 400-600 MW range, which is less than half of the intertie rating.
