Mark Mielke, ATCO, Eastern Alberta Transmission Line
Posted by Vi Hughes on Apr 19, 2017
On Tuesday this week we head from Mark Mielke, pictured, Specialist Engineer with ATCO Electric. He told us about the construction of the recently completed Eastern Alberta Transmission Line. The line runs 485 kilometers from Gibbons/Redwater to just north of Brooks. It supplies power generated in northern Alberta to the Calgary area. The line is a 500 kVolt HVDC (hi voltage direct current) line that currently carries 4.4 million volts. The decision to build this line was made in 2009 at a cost of 1.8 billion dollars. It is the largest project in ATCO’s history. The choice of making it a DC line was made as this technology allows the line to carry more electricity and to have a much smaller footprint on the land. The as built right of way also has the capacity to carry more electricity in the future, without the need for acquiring more land.
The consultation process prior to construction of the actual line was very extensive. It entailed consultations and meetings with land owners, first nations people, pipeline companies, It involved more than 6000 permits for all kinds of various things such as crossings, land acquisitions, and also required environmental plans, historical resource protection plans and impact studies on land and resources. The line crosses 631 pipelines owned by 133 different companies. Environmental protection involved the use of 70,000 rig mats to protect the land from erosion during construction. They also used mobile wash stations to wash down the equipment and vehicles at each tower site before moving on to the next site, in order to prevent the spread of diseases from one field to another.
The line itself consists of two transformer stations, one at each end, to convert AC to DC and then back to AC, 1387 towers, consisting of over 28,000 tons of steel, and 5,200 kilometers of aluminum conductor steel reinforced line. The towers have bases tailored for the type of soil they are built on, hi pile. Caisson or augured grillage bases. The line required 100 ATCO employees and over 800 construction workers to build. A neutral conductor is run along the towers with the line, to keep any current from entering the soil beneath the line, which helps to mitigate any effects on the pipelines that the line crosses. The line also has a hi-tech fiber optic cable strung along it to allow fast (less than 10 millisecond) communications between the operators at each end of the line, and also has a built-in microwave network as a backup communications system.
The transformer stations at either end required special engineering because of the extremely high electrical field inside the transformer hall. The operators work from a separate building connected by 400,000 fiber optic cables to the transformer hall. There are four very large transformers in each station, each weighing 700,000 pounds. The towers were designed specifically for Alberta conditions of wind and snow loading, and were extensively tested prior to use.
The life expectancy of the line is thirty five years, but in practise it could be extended to fifty or more. The cost of the line adds about one dollar per month to the average user’s bill. The line can also be modified to carry more electricity in the future without the need to acquire more land. The line is a unique hi tech wonder that Alberta can be proud of, and gave an Alberta based company an opportunity to develop a lot of new knowledge and skills that can be applied elsewhere.
Mark Mielke