BC Hydro update #13 – Electricity flowing again through BC Hydro’s 500-kilovolt transmission circuit on the Fraser River
VANCOUVER – Good news: electricity is flowing again through BC Hydro’s 500-kilovolt transmission line across the Fraser River near the Port Mann bridge. The line was re-energized this past weekend after it was taken out-of-service in late June following damage in the spring. Over the past few months, BC Hydro has been stabilizing and straightening the 500-kilovolt tower. The line was de-energized to ensure the work could be done safely.
The 500-kilovolt transmission line is key to BC Hydro’s ability to serve local power needs by providing back-up supply and a connection to additional transmission circuits for the high use winter season; and to sell surplus power to markets outside of BC when practical to do so, making it a priority to get the line safely back into service.
BC Hydro has also been working on the 230-kilovolt transmission line running parallel to the 500-kilovolt line after a transmission tower that supports the line fell into the Fraser River on July 4. It is expected that the 230-kilovolt line will be back in service by late fall, using an innovative solution that will not require using the fallen tower.
With both lines being out-of-service this summer, BC Hydro was able to meet local power needs by routing power to customers through different circuits, as adjacent transmission lines in the area are designed to handle additional flow on a short term basis.
Both the 500-kilovolt and 230-kilovolt lines need to be ready to deliver a safe and reliable supply of electricity for this year’s storm season, typically from mid-October to mid-February and to meet the winter peak demand for electricity.
Ongoing restoration
230-kilovolt line (with the fallen tower)
-BC Hydro is restoring the 230-kilovolt line by:
- installing a high-tension, low-sag composite transmission line that will be carried from the tower on the north side of the river to a tower further south and inland from the fallen tower. By using these specialized conductors and stronger towers, BC Hydro will not need to reconstruct the fallen tower as the new lines can be supported over a longer span.
-This work is expected to be completed in November 2011.
500-kilovolt line (previously leaning tower)
-BC Hydro has been stabilizing, repairing and straightening the 500-kilovolt tower by:
- placing 54,000 tonnes of riprap in and around the base of the tower to reinforce the river bed foundation using cranes on barges;
- attaching guy wires from the ground to the waist of the tower;
- installing guy wires to connect the tower to the next closest inland tower (1,743 feet away) using a low-flying helicopter;
- driving eight 100-foot-high steel piles 36-feet into the river bed to allow for the replacement of the foundations; and
- lowering the lines from the top of the tower to the waist
-After the tower was stabilized, BC Hydro used jacks to straighten the tower, remove some of the guy wiring and raise the lines from the waist of the tower back to the top.
-Next spring and after the winter peak season, BC Hydro plans to replace the existing section of line on the 500-kilovolt circuit with the same high-tension, low-sag line technology being used this year on the 230-kilovolt system. These new 500-kilovolt lines will eliminate the need for the once-damaged tower completely, allowing for the subsequent dismantling of the tower.
Background
The 500-kilovoIt line was originally taken out-of-service on June 30 when it was discovered that one of the transmission towers on the south side of the river, carrying the line, was damaged and leaning after it was apparently struck by a large river vessel and then further destabilized by high water flows.
High water levels in the Fraser River this spring and summer also affected a 230-kilovolt transmission line running across the river, parallel to the 500-kilovolt line. A transmission tower with foundations in the Fraser River carrying the 230-kilovolt fell into the water on July 4 after its foundation was compromised, likely due to accelerated erosion caused by high river levels.
For more information and previous tower updates, please visit bchydro.com/mediabulletins.
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Contact:
BC Hydro Media Relations
p. 604.928.6468