January 7, 2013

Ice Storm 1998: 15 years later

What if a storm like the one in 1998 occurred today?

Between January 5 and 10, 1998, Québec experienced exceptionally harsh weather conditions as three successive storms left up to 110 mm of ice over the south of the province. Though robust and well-maintained, the Hydro-Québec grid suffered unprecedented damage.

In the days and weeks that followed, thousands of Hydro-Québec workers, with substantial support from colleagues from Québec companies and neighboring electrical utilities, worked relentlessly to restore power in the regions hardest hit.

By late January, most customers again had power. However, the efforts to ensure a secure power supply did not end there.

Major investments have made the Hydro-Québec grid of today much more robust and better able to withstand the impacts of extreme weather events like the ice storm. As a result, Hydro-Québec is now able to restore service to its customers more quickly.

A Hydro-Québec crew working to repair the grid

In brief
Jean-Pierre Giroux, director of Planning at Hydro-Québec TransÉnergie, provides an overview of the improvements made to the lelectricity transmission and distribution networks.

What has been done since 1998 to minimize the effect of similar weather events in the future?

Like other regions of the world, Québec is not immune to extreme meteorologic conditions. We cannot control Nature but we can control how we act and minimize the impacts of such events. We have invested on a number of fronts to reinforce our power network and improve its performance under harsh climatic conditions.

Thousands of poles, towers and kilometers of lines fell in 1998, often through a domino effect, sometimes increasing by 80% the time it took to restore service to our customers.

Now, our new construction standards limit the potential for that effect. The mechanical strength of our grid has been increased. For instance, by making every tenth tower along a transmission line a very robust anti-cascading tower, we limit the damage that results from the collapse of a single tower.

On the distribution system, we have strengthened poles and their anchoring. We thus ensure that the poles remain intact despite high wind and ice loading. Only the conductors fall, not the poles. Such measures make it possible to restore service more quickly.

Since 1998, all new lines have been built to these tougher engineering standards.

Hydro-Québec has also changed the configuration of its transmission system to make energy sources more secure and to include redundant sources of supply in case of line failures. These  “loops” permit the delivery energy over different paths.

Furthermore, if a satellite substation on the transmission grid is lost, certain distribution lines can provide backup from another substation in order to supply customers.

How does maintenance work help make the grid more robust?

A good example is our effort in the area of vegetation control near transmission and distribution lines, a job that plays a huge role in protecting our power system from the impact of weather events like the ice storm.

Many power failures are caused by contact between branches and power lines. The farther vegetation can be kept away, the better the grid will withstand storms.

If the 1998 storm happened now, how would the power system respond?

Restoration times would be much shorter.

This is because efforts to reinforce the grid, such as creating loops, strengthening facilities and pruning trees, would reduce the number of customers affected and the extent of damage. Repair efforts would thus be more localized and take less time.

Additional information

-Vegetation control
Vegetation control plays a key role in preventing power failures by maintaining clearance around power lines. Efforts were intensified following the 1998 ice storm.

Vegetation growing too close to power lines causes  short circuits, which can  result in power outages.

During wind or ice storms, if trees are too close to distribution lines, falling branches can damage them and greatly increase the time needed to restore electrical service.

This is why Hydro-Québec carries out preventive pruning to ensure that you have reliable service.

For more information on vegetation control:
www.hydroquebec.com/vegetation/en/pop-animation

-R&D’s decisive role
Major research and development efforts to better understand events and to strengthen facilities began immediately after the ice storm and continue today.

Test lines have been built at Hydro-Québec’s research institute, IREQ,  in order to replicate icing conditions, and to test and validate specific designs and parameters.

Certain results have been incorporated into Hydro-Québec construction standards and methods, while various research projects have helped or will help to make the power system more robust.

Innovations include the new generation of insulators now installed to better protect facilities and interphase spacers that curb the effects of galloping, high-amplitude oscillations along overhead conductors.