Western Alberta Transmission Line (WATL)

The Western Alberta Transmission Line (WATL) HVDC project is a power transmission line in Canada, connecting the Genesee area southwest of Edmonton to the Langdon area east of Calgary. This 500 kV HVDC transmission line spans 350 km and was constructed to address the growing electricity demand in Alberta.

Technical Specifications

The WATL project utilizes Line Commutated Converter (LCC) HVDC technology. It was initially installed and commissioned for two-terminal operation with a maximum power transfer capability of 1000 MW. However, the system has been designed to be upgradable to 3000 MW without requiring additional structures or conductors. The project also includes provisions for potential future expansion into a multi-terminal scheme.

The transmission line consists of 995 towers, supporting 3,500 km of transmission line conductor. Approximately 20,000 tons of steel were used in the construction, including about 450 tons of fitting material supplied by Mosdorfer.

Converter Stations

The project includes two 1000 MW, 500 kV monopole HVDC converter stations. These stations are equipped with state-of-the-art control and protection systems that allow precise regulation of power flow through the HVDC system. The control systems can quickly respond to disturbances in the adjoining AC network, helping operators maintain system control and stability during outages.

A notable feature of the WATL project is the installation of a Static Synchronous Compensator (STATCOM) at the southern converter station near Langdon. This STATCOM is used to manage MVAr absorption and production, minimizing the impact on the AC system when the HVDC system's filter banks are switched in and out.

Transmission Line Design

The WATL HVDC transmission line employs a metallic return conductor instead of ground electrodes. This design choice was made to mitigate potential impacts on the numerous oil and gas pipelines in the surrounding area. The line design included careful consideration of conductor and insulator selection, tower design, and minimum electrical clearances.

Testing and Commissioning

The control and protection systems underwent extensive testing using a power system real-time digital simulator (RTDS) at Siemens' factory in Germany. This advanced testing method allowed for accurate simulation of the power grid response to HVDC controls in real-time, enabling modifications to be carried out without risking problems in the actual power system.

Environmental Impact

The HVDC technology used in the WATL project offers lower electrical losses compared to traditional AC transmission. This efficiency is estimated to reduce carbon emissions by approximately 350,000 tonnes, equivalent to removing 65,000 vehicles from Alberta's roads.

Construction and Implementation

The construction of the WATL project faced challenges due to extreme weather conditions, including record snowfall in some areas. To expedite construction, helicopters were utilized for tower erection and line stringing. Cyntech designed, manufactured, and installed helical pile foundations for 137 transmission line structures.

The WATL HVDC project provides increased transfer capability, lower transmission losses, and improved overall system stability compared to an AC equivalent. Its design allows for future expansion and integration with the existing power grid, making it a forward-looking solution for the province's growing energy needs.